RAINS (Another Internet Naming Service) Protocol Specification
ETH Zurich NetSec
Universitaetstrasse 6
Zurich
8092
Switzerland
ietf@trammell.ch
Internet-Draft
This document defines an alternate protocol for Internet name resolution,
designed as a prototype to facilitate conversation about the evolution or
replacement of the Domain Name System protocol. It attempts to answer the
question: “how would we design DNS knowing what we do now,” on the
background of the properties of an ideal naming service described in
.
This document defines an experimental protocol for providing Internet name
resolution services, as a replacement for DNS, called RAINS (RAINS, Another
Internet Naming Service). It is designed as a prototype to facilitate
conversation about the evolution or replacement of the Domain Name System
protocol, and was developed as a name resolution system for the SCION
(“Scalability, Control, and Isolation on Next-Generation Networks”) future
Internet architecture . It attempts to answer the
question: “how would we design the DNS knowing what we do now,” on the
background of the properties of an ideal naming service described in
.
Its architecture () and information model
() are largely compatible with the existing
Domain Name System. However, it does take several radical departures
from DNS as presently defined and implemented:
Delegation from a superordinate zone to a subordinate zone is done solely
with cryptography: a superordinate defines the key(s) that are valid for
signing assertions in the subordinate during a particular time interval.
Assertions about names can therefore safely be served from any infrastructure.
All time references in RAINS are absolute: instead of a time to live, each
assertion’s temporal validity is defined by the temporal validity of the
signature(s) on it.
All assertions have validity within a specific context. A context determines
the rules for chaining signatures to verify validity of an assertion. The
global context is a special case of context, which uses chains from the
global naming root key. The use of context explicitly separates global usage
of the DNS from local usage thereof, and allows other application-specific
naming constraints to be bound to names; see .
Queries are valid in one or more contexts, with specific rules for
determining which assertions answer which queries; see
.
There is an explicit separation between registrant-level names and
sub-registrant-level names, and explicit information about registrars and
registrants available in the naming system at runtime.
Sets of valid characters and rules for valid names are defined on a per-zone
basis, and can be verified at runtime.
Reverse lookups are done using a completely separate tree, supporting
delegations of any prefix length, in accordance with CIDR and
the IPv6 addressing architecture .
Instead of using a custom binary framing as DNS, RAINS uses Concise Binary
Object Representation , partially in an effort to make
implementations easier to verify and less likely to contain potentially
dangerous parser bugs . Like DNS, CBOR messages can be carried
atop any number of substrate protocols; RAINS is presently defined to use TLS
over persistent TCP connections (see ).
The terms MUST, MUST NOT, SHOULD, SHOULD NOT, and MAY, when they appear in
all-capitals, are to be interpreted as defined in .
In addition, the following terms are used in this document as defined:
Authority: An entity which may make assertions about names in a zone, by virtue of holding a secret key which can generate signatures verifiable using a public key associated with a delegation to the zone.
Assertion: A mapping between a name and object(s) of specified types describing the name, signed by an authority for the zone containing the subject name. See .
Subject: The name to which an assertion pertains.
Object: A type/value pair of information about a name within an assertion.
Query: An expression of interest in certain types of objects pertaining to a subject name in one or more contexts. See .
Context: Additional information about the scope in which an assertion or query is valid. See and .
Shard: A group of assertions common to a zone, with common signatures, which may be lexicographically complete for purposes of proving nonexistence of an assertion. See .
Zone: A group of all assertions valid at a given point in time, with common signatures, for a given level of delegation and context within the namespace. See .
RAINS Message: Unit of exchange in the RAINS protocol, containing assertions, shards, zones, queries, and notifications. See .
Notification: A RAINS-internal message section carrying information about the operation of the protocol itself. See .
Authority Service: A service provided by a RAINS Server for publishing assertions by an authority. See .
Query Service: A service provided by a RAINS Server for answering queries on behalf of a RAINS Client. See .
Intermediary Service: A service provided by a RAINS Server for answering queries and providing temporary storage for assertions on behalf of other RAINS Servers. See .
RAINS Server: A server that speaks the RAINS Protocol, and provides on or more services on behalf of other RAINS Servers and/or RAINS Clients. See .
RAINS Client: A client that uses the Query Service of one or more RAINS Servers to retrieve assertions on behalf of applications that wish to connect to named services in the Internet.
The RAINS architecture is simple, and resembles the architecture of DNS. A
RAINS Server is an entity that provides transient and/or permanent storage for
assertions about names, and a lookup function that finds assertions for a
given query about a name, either by searching local storage or by delegating
to another RAINS server. RAINS servers can take on any or all of three roles:
authority service, acting on behalf of an authority to ensure properly
signed assertions are made available to the system (equivalent to an
authoritative server in DNS);
query service, acting on behalf of a client to answer queries with relevant
assertions (equivalent to a recursive resolver in DNS), and to validate
assertions on the client’s behalf; and/or
intermediary service, acting on behalf of neither but providing storage and
lookup for assertions with certain properties for query and authority
servers (partially replacing, but not really equivalent to, caching
resolvers in DNS).
RAINS Servers use the RAINS Protocol defined in this document to exchange
queries and assertions. RAINS Clients use a subset variant of the RAINS Protocol
(called the RAINS Client Protocol) to interact with RAINS Servers providing
query services on their behalf.
Messages in the RAINS Protocol are made up of two kinds of elements: Assertion
and Query.
The information model in this section omits information elements required by
the resolution mechanism itself; these are defined in more detail in
and .
An Assertion is a signed statement about a mapping from a subject name to an
object value, and consists of the following elements:
Context: name of the context in which the assertion is valid;
see below.
Subject: name about which the assertion is made.
Zone: name of the zone in which the assertion is made. The fully qualified
name of the subject is made by appending the zone name to the subject name
with a domain name separator (‘.’).
Type: the type of information about the Subject contained in the
assertion. Each Assertion is about a single type of data.
Object: the data of the indicated type associated with the Subject
Signatures: one or more signatures generated by the authority for the
Assertion. Signatures contain a time interval during which they are considered
valid, and may contain a revocation token allowing them to be revoked before
the end of the time interval. See below.
The Types supported for each assertion are:
Delegation: the authority associated with the zone identified by the name
(roughly equivalent to the DNSSEC DS RRTYPE). The Object contains a public
key by which the authority can be identified.
Redirection: The name(s) of one or more a RAINS servers providing authority
service for the authority associated with the zone (roughly equivalent to
the DNSSEC NS RRTYPE, but not always consulted directly during resolution).
The Object contains a set of names.
Address: one or more addresses associated with the name (replaces DNS A and
AAAA RTYPEs). The Object contains a set of Addresses. An Address is an
{address-family, value} tuple.
Service-Info: one or more layer 4 ports and hostnames associated with a
service name (replaces DNS SRV RRTYPE). The object contains a {hostname,
port-number, priority tuple}.
Name: one or more names associated with the name (roughly equivalent to DNS
CNAME). The Object contains a set of names.
Certificate: a certificate which must appear at a specified location in the
certificate chain presented on a connection attempt with the named entity
(roughly equivalent to DNS TLSA).
Zone-Nameset: an expression of the set of names allowed within a zone; e.g.
Unicode scripts or codepages in which names in the zone may be issued. This
allows a zone to set policy on names in support of the distinguishability
property in that can be checked by RAINS
servers at runtime. An assertion about a Subject within a Zone whose
name is not allowed by a valid signed Zone-Nameset expression is taken to be
invalid, even if it has a valid signature.
Zone-Registrar: Information about the organization that caused a Subject name
to exist, for registrant-level names.
Zone-Registrant: Information about the organization responsible for a
Subject name, for registrant-level names.
Infrastructure Key: Information about public keys used for object security
within the RAINS infrastructure itself. The Object contains a public key by
which a named RAINS server can be identified.
External Key: Information about public keys used for additional signatures
on assertions. The external key is usually discovered outside RAINS, and can
be verified by comparison with the key stored in a RAINS assertion. The
Object contains an external public key.
For a given {subject, type} tuple, multiple assertions can be valid at a given
point in time; the union of the object values of all of these assertions is
considered to be the set of valid values at that point in time.
Assertion contexts are used to determine the validity of the signature by the
declared authority as follows:
The global context is identified by the special context name `.’. Assertions
in the global context are signed by the authority for the subject name. For
example, assertions about the name simplon.inf.ethz.ch in the global context
are only valid if signed by the relevant authority inf.ethz.ch.
A local context is associated with a given authority. The authority-part and
the context-part of a local context name are divided by a context marker
(‘cx–’). The authority-part directly identifies the authority whose key was
used to sign the assertion; assertions within a local context are only valid
if signed by the identified authority. Authorities have complete control
over how the contexts under their namespaces are arranged, and over the names
within those contexts.
Assertion context is the mechanism by which RAINS provides explicit
inconsistency (see section 5.3.2 of ). Some
examples illustrate how context works:
For the common split-DNS case, an enterprise could place names for machines
on its local networks within a separate context. E.g., a workstation could
be named simplon.cab.inf.ethz.ch within the context
staff-workstations.cx–.inf.ethz.ch. Assertions about this name would
be signed by the authority
for inf.ethz.ch. Here, the context serves simply as a marker, without enabling
an alternate signature chain: note that the name simplon.cab.inf.ethz.ch can
be validly signed by the authority for inf.ethz.ch if no delegation exists
for cab.inf.ethz.ch. The context simply marks this assertion as internal. This
allows a client making requests of local names to know they are local, and
for local resolvers to manage visibility of assertions outside the
enterprise: explicit context makes accidental leakage of both queries and
assertions easier to detect and avoid.
Contexts make captive-portal interactions more explicit: a captive portal
resolver could respond to a query for a common website (e.g. www.google.ch)
with a signed response directed at the captive portal, but within a context
identifying the location as well as the ISP (e.g.
sihlquai.zurich.ch.cx–.starbucks.access.some-isp.net.). This response will
be signed by the authority for starbucks.access.some-isp.net. This
signature achieves two things: first, the client knows the result for
www.google.ch is not globally valid; second, it can present the user with
some indication as to the identity of the captive portal it is connected to.
Further examples showing how context can be used in queries as well are given
in below.
Developing conventions for assertion contexts for different situations will
require implementation and deployment experience, and is a subject for future
work.
A signature over an assertion contains the following information elements:
Algorithm: identifier of the algorithm used to generate the signature.
Valid-Since: a timestamp of the start of validity of this signature.
Valid-Until: a timestamp of the end of validity of this signature.
Signature: the cryptographic signature itself, whose format is determined by
the algorithm used.
Revocation-Token: an optional revocation token for this signature, which
allows a signature to be replaced or removed before the end of its validity.
Revocation tokens are generally based on hash chains, meaning that a
signature with a revocation token “down” the chain from a given token
supercedes it. The format and mechanism used by the revocation token is
determined by the alogrithm used. (Note that revocation is a presently
unspecified feature in the protocol; see .)
The signature protects all the information in an assertion as well as its own
valid-since and valid-until values and the revocation token; it does not
protect other signatures on the assertion.
Assertions may also be grouped and signed as a group. A shard is a set of
assertions subject to the same authority within the same context, protected by
one or more signatures over all assertions within the shard. A shard may have
an additional property that given a subject and an authenticated shard, it can
be shown that either an assertion with a given name and type exists within the
shard or does not exist at all.
A shard has the following information elements:
Context: name of the context in which the assertions in the shard are valid;
see above.
Zone: name of the zone in which the assertions are made.
Content: a set of assertions sharing the context and zone.
Signatures: one or more signatures generated by the authority for the
shard; see .
Complete-Flag: if true, the shard is lexicographically complete, and subject
names that sort such that they would be within the shard if they existed,
but are not in the shard, can be assumed not to exist.
For efficiency’s sake, information elements within a shard common to all
assertions (zone, context, signature) within the shard may be omitted from the
assertions themselves.
A zone is the entire set of shards subject to a given
authority within a given context. There are three kinds of zones;
treating these zones differently may allow lookup protocol
optimizations:
Zones containing only delegation assertions are delegation-only zones.
Delegation-only zones are not relevant as part of an assertion lookup, other
than for discovering and verifying authority. Top-level domains are
generally delegation-only.
Zones containing no delegation assertions are final zones. Final zones are
not relevant as part of an authority discovery.
Zones containing at least one delegation assertion and at least one
assertion that is not a delegation assertion are mixed zones. No
optimizations are available for mixed zones.
A zone has the following information elements:
Context: name of the context in which the assertions in the zone are valid;
see above.
Zone: name of the zone.
Content: a set of assertions and/or shards sharing the context and zone.
Signatures: one or more signatures generated by the authority for the
shard; see .
Kind: delegation-only, final, or mixed; see above.
A zone may make an assertion about itself by using an empty subject name. This
facility can be used for any assertion type, but is especially useful for
self-signing root zones.
A query is a request for a set of assertions supporting a conclusion about a
given subject-object mapping. It consists of the following information
elements:
Context: The context(s) in which assertions answering the
query will be accepted; see below.
Qualified-Subject: the name about which the query is made. The subject name
in a query must be fully-qualified.
Types: a set of assertion types the querier is interested in.
Valid-Until: an optional client-generated timestamp for the query after
which it expires and should not be answered.
Query Token: a client-generated token for the query, which can be used
in the answer to refer to the query.
Options: a set of options by which a client may specify tradeoffs
(e.g. privacy for performance).
A query expresses interest about all the given types of assertion in all the
specified contexts; more complex expressions of which types in which contexts
must be asked using multiple queries. Preferences for tradeoffs (freshness,
bandwidth efficiency, latency, privacy preservation) in servicing a query may
be bound to the query using query options.
Context is used in queries as it is in assertions (see
). Assertion contexts in an answer to a query have to
match the context in the query in order to respond to a query. The Context
section of a query contains the context of desired assertions; a special “any”
context (represented by the empty string) indicates that assertions in any
context will be accepted.
Query contexts can also be used to provide additional information to RAINS
servers about the query. For example, context can provide a method for
explicit selection of a CDN server not based on either the client’s or the
resolver’s address (see ). Here, the CDN creates a context for
each of its content zones, and an external service selects appropriate
contexts for the client based not just on client source address but passive
and active measurement of performance. Queries for names at which content
resides can then be made within these contexts, with the priority order of
the contexts reflecting the goodness of the zone for the client. Here, a
context might be zrh.cx–.cdn-zones.some-cdn.com for names of servers
hosting content in a CDN’s Zurich data center, and a client could represent
its desire to find content nearby by making queries in the zrh.cx–,
fra.cx– (Frankfurt), and ams.cx– (Amsterdam) contexts within cdn-zones
.some-cdn.com. In all cases, the assertions themselves will be signed by the
authority for cdn-zones.some-cdn.com, accurately representing that it is
the CDN, not the owner of the related name in the global context, that is
making the assertion.
As with assertion contexts, developing conventions for query contexts for
different situations will require implementation and deployment experience,
and is a subject for future work.
An answer consists of a set of assertions, shards, and/or zones which respond
to a query. If the query contained a token, it is bound to that query via the
token.
The content of an answer depends on whether the answer is positive or negative.
A positive answer contains the information requested in the smallest atomic
container that can be found, usually a single assertion. A negative answer
contains the information used to verify it; either a shard with the
Complete-Flag set, an entire Zone, or a Zone-Nameset assertion showing the name
is illegal within the zone.
A query is taken to have an inconclusive answer when no answer returns to the
querier before the query’s Valid-Until time.
In contrast to the current domain name system, information about addresses is
stored in a completely separate tree, keyed by address and prefix. An address
assertion consists of the following elements:
Context: name of the context in which the assertion is valid;
see .
Subject: address about which the assertion is made, consisting of an address
family, address, and prefix length. A subject may be a network address
(where the prefix length is less than the address length for the given
address family) or a host address (where the prefix length is equal to the
address length for the given address family)
Type: the type of information about the Subject contained in the
assertion. Each Assertion is about a single type of data.
Object: the data of the indicated type associated with the Subject
Signatures: one or more signatures generated by the authority for the
Assertion. Signatures contain a time interval during which they are considered
valid, and may contain a revocation token allowing them to be revoked before
the end of the time interval, as in .
The following object types are available:
Delegation: the authority associated with the subject network address.
The Object contains a public key by which the authority can be identified. Only available for network address subjects.
Redirection: The name(s) of one or more a RAINS servers providing authority
service for the authority associated with the subject network address.
The Object contains a set of names. Only available for network address subjects.
Name: one or more names associated with the subject network address.
The Object contains a set of names. Only available for host address subjects.
Zone-Registrant: Information about the organization responsible for a
network. Only available for network address subjects.
Assertions about addresses can be grouped into Zones. An address Zone has the following information elements:
Context: name of the context in which the assertions in the zone are valid;
see .
Zone: subject address of the zone, consisting of an address family,
address, and prefix length. The prefix length must be less than the address
length for the given address family.
Content: a set of assertions and/or shards sharing the context and zone.
Signatures: one or more signatures generated by the authority for the
shard; see .
Queries for addresses are similar to those for names, and consist of the following information elements:
Context: Context in which the query is made; this must match the assertion
context as in .
Subject: the address about which the query is made, consisting of an address
family, address, and prefix length.
Types: a set of assertion types the querier is interested in, as above.
Valid-Until: an optional client-generated timestamp for the query after
which it expires and should not be answered.
Query Token: a client-generated token for the query, which can be used
in the answer to refer to the query.
Just as in forward Assertions, Assertion contexts are used in address
assertions to determine the scope of an address assertion, and the signature
chain used to verify it.
The global addressing context for each address family is identified by the
special context name `.’. For both IPv4 and IPv6 addresses, this is rooted at IANA, which delegates to the RIRs, which then delegates to LIRs and to address-holding registries.
Local contexts associated with a given authority in a forward tree can
also make assertions about addresses. As with contexts in forward
assertions, the authority-part and
the context-part of a local context name are divided by a context marker
(‘cx–’). The authority-part directly identifies the authority whose key was
used to sign the assertion; assertions within a local context are only valid
if signed by the identified authority. Authorities have complete control
over how the contexts under their namespaces are arranged, and over the names
within those contexts.
Each local context may have a root address space zone (0/0), but these root
address spaces may only delegate addresses that are reserved for local use
. Local context assertions for other addresses are
invalid.
The RAINS data model is a relatively straightforward mapping of the
information model in to the Concise Binary Object
Representation (CBOR) , with an outer message type providing a
mechanism for future capabilities-based versioning and recognition of a
message as a RAINS message.
Messages, assertions, shards, zones, queries, and notifications are each
represented as a CBOR map of integer keys to values, which allows each of
these types to be extended in the future, as well as the addition of non-
standard, application-specific information to RAINS messages and data items. A
common registry of map keys is given in . RAINS implementations
MUST ignore map keys the do not understand. Integer map keys in the range -22
to +23 are reserved for the use of future versions or extensions to the RAINS
protocol.
Message contents, signatures and object values are implemented as type-
prefixed CBOR arrays with fixed meanings of each array element; the structure
of these lower-level elements can therefore not be extended. Message section
types are given in , object types in , and signature
algorithms in .
The meaning of each of the integer keys in message, zone, shard, assertion,
and notification maps is given in the symbol table below:
Code
Name
Description
0
signatures
Signatures on a message or section
1
capabilities
Capabilities of server sending message
2
token
Token for referring to a data item
3
subject-name
Subject name in an assertion
4
subject-zone
Zone name in an assertion
5
subject-addr
Subject address in address assertion or zone
6
context
Context of an assertion or query
7
objects
Objects of an assertion
8
query-name
Fully qualified name for a query
10
query-types
Acceptable object types for query
11
shard-range
Lexical range of Assertions in Shard
12
query-expires
Absolute timestamp for query expiration
13
query-opts
Set of query options requested
21
note-type
Notification type
22
note-data
Additional notification data
23
content
Content of a message, shard, or zone
All interactions in RAINS take place in an outer envelope called a Message,
which is a CBOR map tagged with the RAINS Message tag (hex 0xE99BA8, decimal
15309736).
A Message map MAY contain a signatures (0) key, whose value is an array of
Signatures over the entire message as defined in , to be
verified against the infrastructure key for the RAINS Server originating the
message.
A Message map MAY contain a capabilities (1) key, whose value is described in
{#cbor-capabilities}.
A Message map MUST contain a token (2) key, whose value is a byte array of
maximum length 32. See .
A Message map MUST contain a content (23) key, whose value is an array of
Message Sections; a Message Section is either an Assertion, Shard, Zone, or
Query.
Each Message Section in the Message’s content value MUST be a two-element
array. The first element in the array is the message section type, encoded as
an integer as in . The second element in the array is a message
section body, a CBOR map defined as in the subsections shown in :
Code
Name
Description
1
assertion
Assertion (see )
-1
revassertion
Address Assertion (see )
2
shard
Shard (see )
3
zone
Zone (see )
-3
revzone
Address Zone (see )
4
query
Query (see )
-4
revquery
Address Query (see
23
notification
Notification (see )
An Assertion body is a map. The keys present in this map depend on whether the
Assertion is contained in a Message Section or in a Shard or Zone.
Assertions contained in Message Sections are “bare Assertions”. Since they
cannot inherit any values from their containers, they MUST contain the
signatures (0), subject-name (3), subject-zone (4), context (6), and objects
(7) keys.
Assertions within a Shard or Zone are “contained Assertions”, and can inherit
values from their containers. A contained Assertion MUST contain the subject-
name (3) and objects (7) keys. It MAY contain subject-zone (4) and context (6)
keys, but in this case the values of these keys MUST be identical to the
values in the containing Shard or Zone.
A contained Assertion SHOULD contain the signatures (0) key, since an unsigned
contained Assertion cannot be used by a RAINS server to answer a query; it
must be returned in a signed Shard or Zone.
The value of the signatures (0) key, if present, is an array of one or more
Signatures as defined in . If not present, the containing
Shard or Zone MUST be signed. Signatures on a contained Assertion are
generated as if the inherited subject-zone and context values are present in
the Assertion, whether actually present or not. The signatures on the
Assertion are to be verified against the appropriate key for the Zone
containing the Assertion in the given context, as described in
.
The value of the subject-name (3) key is a UTF-8 encoded string
containing the name of the subject of the assertion. The subject name never
contains the zone in which the subject name; the fully-qualified name is
obtained by joining the subject-name to the subject-zone with a ‘.’ character.
The subject-name must be valid according to the nameset expression for the
zone, if any.
The value of the subject-zone (4) key, if present, is a UTF-8 encoded string
containing the name of the zone in which the assertion is made. If not
present, the zone of the assertion is inherited from the containing Shard or Zone.
The value of the context (6) key, if present, is a UTF-8 encoded string
containing the name of the context in which the assertion is valid. If not
present, the context of the assertion is inherited from the containing Shard
or Zone.
The value of the objects (7) key is an array of objects, as defined in
.
A Shard body is a map. The keys present in the map depend on whether the Shard
is contained in a Message Section or in a Zone.
Shards contained in Message Sections are “bare Shards”. Since they cannot
inherit any values from their contained Zone, they MUST contain the content
(23), signatures (0), subject-zone (4), context (6), and may contain the shard-range (11) key.
Shards within a Zone are “contained Shards”, and can inherit values from their
containing Zone. A contained Shard MUST contain the content (23) key, and MAY
contain the shard-range(11) key. It MAY contain subject- zone (4) and context
(6) keys, but in this case the values of these keys MUST be identical to the
values in the containing Zone.
A contained Shard SHOULD contain the signatures (0) key if it also contains a
shard-range (11) key, since an unsigned contained Shard cannot be used by a
RAINS server to answer a query for nonexistence; it must be returned in a
signed Zone.
The value of the content (23) key is an array of Assertion bodies as defined in
{#cbor-assertion}.
The value of the signatures (0) key, if present, is an array of one or more
Signatures as defined in . If not present, the containing
Zone MUST be signed. Signatures on a contained Shard are generated as if the
inherited subject-zone and values are present in the Shard, whether actually
present or not. The signatures on the Shard are to be verified against the
appropriate key for the Zone containing the Shard in the given context, as
described in .
The value of the subject-zone (4) key, if present, is a UTF-8 encoded string
containing the name of the zone in which the Assertions within the Shard is
made. If not present, the zone of the assertion is inherited from the
containing Zone.
The value of the context (6) key, if present, is a UTF-8 encoded string
containing the name of the context in which the Assertions within the Shard
are valid. If not present, the context of the assertion is inherited from the
containing Zone.
If the shard-range (11) key is present, the the shard is lexicographically complete
within the range described in its value: a mapping for a (subject-name,
object-type) pair that should be between the two values given in the range but
is not is asserted to not exist. Lexicographic sorting is done on subject names
by ordering Unicode codepoints in ascending order; ordering on object types is
done via their code values in in ascending order.
The shard-range value MUST be a two element array of strings or nulls
(subject-name A, subject-name B). A must lexicographically sort before B, but
neither subject name need be present in the shard’s contents. If A is null,
the shard begins at the beginning of the zone. If B is null, the shard ends at
the end of the zone. The shard MUST NOT contain any assertions whose subject
names sort before A or after B. In addition, the authority for the shard belongs to
MUST NOT make any assertions during the period of validity of the shard’s
signatures that would fall between subject-name A and subject-name B inclusive
that are not contained within the shard
(see ).
If the shard-range key is not present, the shard is not lexicographically
complete and MUST NOT be used to make assertions about nonexistance.
A Zone body is a map. Zones MUST contain the content (23), signatures (0),
subject-zone (4), and context (6) keys.
Signatures on the Zone are to be verified against the appropriate key for the
Zone in the given context, as described in .
The value of the content (23) key is an array of Shard bodies as defined in
{#cbor-shard} and/or Assertion bodies as defined in {#cbor-assertion}.
The value of the subject-zone (4) key is a UTF-8 encoded string
containing the name of the Zone.
The value of the context (6) key is a UTF-8 encoded string
containing the name of the context for which the Zone is valid.
A Query body is a map. Queries MUST contain the the token (2), query-name (8),
context (6), and query-types (10) keys. Queries MAY contain the query-
expires (12) and query-opts (13) keys.
The value of the token (2) key, is a byte array of maximum length
32. Future messages or notifications containing answers to this query MUST
contain this token, if present. See .
The value of the context (6) key is a UTF-8 encoded string containing the name
of the context to which a query pertains. A zero-length string indicates that
assertions will be accepted in any context.
The value of the query-types (10) key is an array of integers encoding the
type(s) of objects (as in ) acceptable in answers to the query.
All values in the query-type array are treated at equal priority: [2,3] means
the querier is equally interested in both IPv4 and IPv6 addresses for the
query-name. An empty query-types array indicates that objects of any type are
acceptable in answers to the query.
The value of the query-expires (12) key, if present, is a CBOR integer
counting seconds since the UNIX epoch UTC, identified with tag value 1 and
encoded as in section 2.4.1 of . After the query-expires time, the
query will have been considered not answered by the original issuer.
The value of the query-opts (13) key, if present, is an array of integers in
priority order of the querier’s preferences in tradeoffs in answering the
query, as in .
Code
Description
1
Minimize end-to-end latency
2
Minimize last-hop answer size (bandwidth)
3
Minimize information leakage beyond first hop
4
No information leakage beyond first hop: cached answers only
5
Expired assertions are acceptable
6
Enable query token tracing
7
Disable verification delegation (client protocol only)
8
Suppress proactive caching of future assertions
Options 1-5 specify performance/privacy tradeoffs. Each server is free to
determine how to minimize each performance metric requested; however, servers
MUST NOT generate queries to other servers if “no information leakage” is
specified, and servers MUST NOT return expired assertions unless “expired
assertions acceptable” is specified.
Option 6 specifies that a given token (see ) should be used on
all queries resulting from a given query, allowing traceability through an
entire RAINS infrastructure. It is meant for debugging purposes.
By default, a client service will perform verification of negative queries and
return a 404 No Assertion Exists for queries with a consistent proof of non-
existence, within a message signed by the query service’s infrakey. Option 7
disables this behavior, and causes the query service to return the shard
proving nonexistence for verification by the client. It is intended to be used
with untrusted query services.
Option 8 specifies that a querier’s interest in a query is strictly ephemeral,
and that future assertions related to this query SHOULD NOT be proactively
pushed to the querier.
Assertions about addresses are similar to assertions about names, but keyed by
address and restricted in terms of the objects they can contain. An Address
Assertion body is a map. The keys present in this map depend on whether the
Assertion is contained in a Message Section or in an Address Zone.
Address Assertions contained in Message Sections are “bare Address
Assertions”, and MUST contain the signatures (0), subject-addr (5),
context (6), and objects (7) keys.
Address Assertions contained in an Address Zone are “contained Address
Assertions”, and can inherit their context from and be signed within their
containing Zone. A contained Address Assertion MUST contain the
subject-addr (5) and objects (7) keys. It MAY contain the context (6) key, but in
this case the value of this keys MUST be identical to the value in the
containing Address Zone.
A contained Address Assertion SHOULD contain the signatures (0) key, since an
unsigned contained Address Assertion cannot be used by a RAINS server to
answer a query; it must be returned in a signed Address Zone.
The value of the signatures (0) key, if present, is an array of one or more
Signatures as defined in . If not present, the containing
Address Zone MUST be signed. Signatures on a contained Address Assertion are
generated as if the inherited context value are present in
the Assertion, whether actually present or not. The signatures on the
Assertion are to be verified against the appropriate key for the Address Zone
containing the Assertion in the given context, as described in
.
The value of the subject-addr (5) key is a three element CBOR array. The first
element of the array is the address family encoded as an object type, 2 for
IPv6 addresses and 3 for IPv4 addresses. The second element is the prefix
length encoded as an integer, 0-128 for IPv6 and 0-32 for IPv4. The third
element is the address, encoded as in . Subject addresses with
the maximum prefix length for the address family are subject host addresses,
and are nameable; subject addresses with less than the maximum prefix length
are subject network addresses, and are delegatable.
The value of the context (6) key, if present, is a UTF-8 string
containing the name of the context in which the Address Assertion is valid. If
not present, the context of the Address Assertion is inherited from the
containing Address Zone. See .
The value of the objects (7) key is an array of objects, as defined in
. Only object types redirection, delegation, and registrant are
available for subject network addresses, and only object type name is
available for subject host addresses.
Assertions about addresses can be grouped into zones, where all the assertions
within the zone are contained within the zone’s address. These Address Zones
are similar to Zones containing assertions about names, but are keyed by
network address and restricted in their semantics.
An Address Zone body is a map. Zones MUST contain the content (23), signatures (0),
subject-addr (5), and context (6) keys.
Signatures on the Zone are to be verified against the appropriate key for the
Zone in the given context, as described in .
The value of the subject-addr (5) key is a three element CBOR array. The first
element of the array is the address family encoded as an object type, 2 for
IPv6 addresses and 3 for IPv4 addresses. The second element is the prefix
length encoded as an integer, 0-127 for IPv6 and 0-31 for IPv4. The third
element is the address, encoded as in . Only subject network
addresses are acceptable for Address Zones.
The value of the content (23) key is an array of Address Assertion bodies as
defined in {#cbor-revassert}. The Address Assertions within the content array
MUST fall completely within the network designated by the subject-addr value.
The value of the context (6) key is a UTF-8 encoded string
containing the name of the context for which the Zone is valid.
Queries for assertions about addresses are similar to queries for assertions
about names, but have semantic restrictions similar to those for Address
Assertions and Address Zones. An address query may have only one context.
An Address Query body is a map. Queries MUST contain the the token (2), subject-addr (5),
context (6), and query-types (10) keys. Queries MAY contain query-opts
(13) and query-expires (12) keys.
The value of the token (2) key, is a byte array of maximum length
32. Future messages or notifications containing answers to this query MUST
contain this token, if present. See .
The value of the subject-addr (5) key is a three-element CBOR array. The first
element of the array is the address family encoded as an object type, 2 for
IPv6 addresses and 3 for IPv4 addresses. The second element is the prefix
length encoded as an integer, 0-128 for IPv6 and 0-32 for IPv4. The third
element is the address, encoded as in .
The value of the context (6) key is a UTF-8 encoded string containing the name
of the context for which the Query is valid. Unlike queries for names, queries
for Address Queries can only pertain to a single context.
See for more.
The value of the query-expires (12) key, if present, is a CBOR integer
counting seconds since the UNIX epoch UTC, identified with tag value 1 and
encoded as in section 2.4.1 of . After the query-expires time, the
query will have been considered not answered by the original issuer.
The value of the query-opts (13) key, if present, is an array of integers in
priority order of the querier’s preferences in tradeoffs in answering the
query, as in . See for more.
Any Address Assertion relating to an address containing the address queried
for is considered to respond to the query, with more-specific prefixes being
preferred over less-specific.
Notification Message Sections contain information about the operation of the
RAINS protocol itself. A Notification Message Section body is a map which MUST
contain the token (2) and note-type (21) keys and MAY contain the note-data
(22) key. The value of the note-type key is encoded as an integer as in the
.
Code
Description
100
Connection heartbeat
399
Capability hash not understood
400
Malformed message received
403
Inconsistent message received
404
No assertion exists (client protocol only)
413
Message too large
500
Unspecified server error
501
Server not capable
504
No assertion available
Note that the status codes are chosen to be mnemonically similar to status
codes for HTTP . Details of the meaning of each status code are
given in .
The value of the token (2) key is a byte array of maximum length 32, which
MUST contain the token of the message or query to which the notification is a
response. See .
The value of the note-data (22) key, if present, is a UTF-8 encoded string
with additional information about the notification, intended to be displayed
to an administrator to help debug the issue identified by the negotiation.
Objects are encoded as arrays in CBOR, where the first element is the type of
the object, encoded as an integer in the following table:
Code
Name
Description
1
name
name associated with subject
2
ip6-addr
IPv6 address of subject
3
ip4-addr
IPv4 address of subject
4
redirection
name of zone authority server
5
delegation
public key for zone delgation
6
nameset
name set expression for zone
7
cert-info
certificate information for name
8
service-info
service information for srvname
9
registrar
registrar information
10
registrant
registrant information
11
infrakey
public key for RAINS infrastructure
12
extrakey
external public key for subject
A name (1) object contains a name associated with a name as an alias. It is
represented as a three-element array. The second element is a fully-qualified
name as a UTF-8 encoded string. The third type is an array of object type
codes for which the alias is valid, with the same semantics as the query-types
(9) key in queries (see ).
An ip6-addr (2) object contains an IPv6 address associated with a name. It is
represented as a two element array. The second element is a byte array of
length 16 containing an IPv6 address in network byte order.
An ip4-addr (3) object contains an IPv4 address associated with a name. It is
represented as a two element array. The second element is a byte array of
length 4 containing an IPv4 address in network byte order.
A redirection (4) object contains the fully-qualified name of a RAINS
authority server for a named zone. It is represented as a two-element array.
The second element is a fully-qualified name of an RAINS authority server as a
UTF-8 encoded string.
A delegation (5) object contains a public key used to generate signatures
on assertions in a named zone, and by which a delegation of a name within a
zone to a subordinate zone may be verified. It is represented as an N-element
array. The second element is a signature algorithm identifier as in
. Additional elements are as defined in
for the given algorithm identifier.
A nameset (6) object contains an expression defining which names are allowed
and which names are disallowed in a given zone. It is represented as a two-
element array. The second element is a nameset expression to be applied to
each name element within the zone without an intervening delegation, as
defined in
A cert-info (7) object contains an expression binding a certificate or
certificate authority to a name, such that connections to the name must either
use the bound certificate or a certificate signed by a bound authority. It is
represented as an five-element array, as defined in .
A service-info (8) object gives information about a named service. Services
are named as in . It is represented as a four-element array. The
second element is a fully-qualified name of a host providing the named service
as a UTF-8 string. The third element is a transport port number as a positive
integer in the range 0-65535. The fourth element is a priority as a positive
integer, with lower numbers having higher priority.
A registrar (9) object gives the name and other identifying information of the
registrar (the organization which caused the name to be added to the
namespace) for organization-level names. It is represented as a UTF-8 string
of maximum length 256 bytes containing identifying information chosen by the
registrar according to the registry’s policy.
A registrant (10) object gives information about the registrant of an
organization-level name. It is represented as a UTF-8 string with a maximum
length of 4096 bytes containing this information, with a format chosen by the
registrar according to the registry’s policy.
An infrakey (11) object contains a public key used to generate signatures on
messages by a named RAINS server, by which a RAINS message signature may be
verified by a receiver. It is identical in structure to a delegation object,
as defined in . Infrakey signatures are especially useful
for clients which delegate verification to their query servers to authenticate
the messages sent by the query server.
An extrakey (12) object contains a public key used to generate signatures on
assertions in a named zone outside of the normal delegation chain. It is
identical in structure to a delegation object, as defined in {{cbor-
signature}}. An extrakey may be matched with a public key obtained through
other means for additional authentication of an assertion. Extrakeys are
different from delegation keys in that they may not be used in the delegation
chain: an extrakey signature is valid only on assertions of object types other
than delegation.
A cert-info object contains information about the certificate(s) that can be
used to authenticate a transport-layer association with a named entity. It is
encoded as a file-element array. The first element is the RAINS object type
(7). The second element is the protocol family specifier, describing the
cryptographic protocol used to connect, as defined in . The
protocol family defines the format of certificate data to be hashed. The third
element is the certificate usage specifier as in , describing
the constraint imposed by the assertion. These are defined to be compatible
with Certificate Usages in the TLSA RRTYPE for DANE . The fourth
element is the hash algorithm identifier, defining the hash algorithm used to
generate the certificate data. The fifth item is the data itself, whose format
is defined by the protocol family and hash algorithm.
Code
Protocol family
Certificate format
0
Unspecified
Unspecified
1
Transport Layer Security (TLS)
Protocol family 0 leaves the protocol family unspecified; client validation
and usage of cert-info assertions, and the protocol used to connect, are up to
the client, and no information is stored in RAINS. Protocol family 1 specifies
Transport Layer Security version 1.2 or a subsequent version,
secured with PKIX certificates.
Code
Certificate usage
2
Trust Anchor Certificate
3
End-Entity Certificate
A trust anchor certificate constraint specifies a certificate that MUST appear
as the trust anchor for the certificate presented by the subject of the
assertion on a connection attempt. An end-entity certificate constraint
specifies a certificate that MUST be presented by the subject of the assertion
on a connection attempt.
Code
Hash/HMAC
Notes
0
None
Data contains full certificate
1
sha-256
Data contains SHA-256 hash (32 bytes)
2
sha-512
Data contains SHA-512 hash (64 bytes)
3
sha-384
Data contains SHA-384 hash (48 bytes)
Code 0 is used to store full certificates in RAINS assertions, while other
codes are used to store hashes for verification.
For example, in a cert-info object with values [ 7, 1, 3, 3, (data) ], the
data would be a 48 SHA-384 hash of the ASN.1 DER-encoded X.509v3 certificate
(see Section 4.1 of ) to be presented by the endpoint on a
connection attempt with TLS version 1.2 or later.
The nameset expression is represented as a UTF-8 string encoding a modified POSIX
Extended Regular Expression format (see POSIX.2) to be applied to each element
of a name within the zone. A name containing an element that does not match
the valid nameset expression for a zone is not valid within the zone, and the
nameset assertion can be used to prove nonexistence.
The POSIX character classes :alnum:, :alpha:, :ascii:, :digit:, :lower:, and :upper: are available in these regular expressions, where:
:lower: matches all codepoints within the Unicode general category “Letter, lowercase”
:upper: matches all codepoints within the Unicode general category “Letter, uppercase”
:alpha: matches all codepoints within the Unicode general category “Letter”.
:digit: matches all codepoints within the Unicode general category “Number, decimal digit”
:alnum: is the union of :alpha: and :digit:
:ascii: matches all codepoints in the range 0x20-0x7f
In addition, each Unicode block is available as a character class, with the syntax :ublkXXXX: where XXXX is a 4 or 5 digit, zero-prefixed hex encoding of the first codepoint in the block. For example, the Cyrillic block is available as :ublk0400:.
Unicode escapes are supported in these regular expressions; the sequence
\uXXXX where XXXX is a 4 or 5 digit, possibly zero-prefixed hex encoding of
the codepoint, is substituted with that codepoint.
Set operations (intersection and subtraction) are available on character
classes. Two character class or range expressions in a bracket expression
joined by the sequence && are equivalent to the intersection of the two
character classes or ranges. Two character class or range expressions in a
bracket expression joined by the sequence – are equivalent to the subtraction
of the second character class or range from the first.
For example, the nameset expression:
[[:ublk0400:]&&[:lower:][:digit:]]+
matches any name made up of one or more lowercase Cyrillic letters and digits. The same expression can be implemented with a range instead of a character class:
[\u0400-\u04ff&&[:lower:][:digit:]]+
Messages, queries, and notifications all contain an opaque token (2) key,
whose content is a byte array of maximum length 32, and is used to link
Messages to the Queries they respond to, and Notifications to the Messages
they respond to. Tokens MUST be treated as opaque values by RAINS servers.
A Message sent in response to a Query MUST contain the token in that Query.
Otherwise, the Message SHOULD contain a token selected by the server
originating it, so that future Notifications can be linked to the message
causing it. Likewise, a Notification sent in response to a Message MUST
contain the token from the Message causing it.
When a server creates a new query to forward to another server in response to
a query it received, it MUST NOT use the same token on the delegated query
as on the received query, unless option 6 Enable Tracing is present in the
received, in which case it MUST use the same token.
RAINS supports multiple signature algorithms and hash functions for signing
assertions for cryptographic algorithm agility . A RAINS signature
algorithm identifier specifies the signature algorithm; a hash function for
generating the HMAC and the format of the encodings of the signature
values in Assertions, Shards, Zones, and Messages, as well as of public key
values in delegation objects.
RAINS signatures have three common elements: the algorithm identifier, a
valid-since timestamp, and a valid-until timestamp.
Signatures are represented as an array of these three values followed by
additional elements containing the signature data itself, according to the
algorithm identifier.
Valid-since and valid-until timestamps are represented as CBOR integers
counting seconds since the UNIX epoch UTC, identified with tag value 1 and
encoded as in section 2.4.1 of . A signature MUST have a
valid-until timestamp. If a signature has no specified valid-since time (i.e.,
is valid from the beginning of time until its valid-until timestamp), the
valid-since time MAY be null (as in Table 2 in Section 2.3 of ).
Signatures in RAINS are generated over a normalized serialized CBOR object (a
Message; or an Assertion, Shard, or Zone section body). To normalize and
serialize an object for signing:
Serialize the object with a stub for the signature to be generated:
Strip all other signatures during serialization by omitting all signatures
(0) keys and their values. When signing a shard or zone, the signatures on
contained assertions, if present, must be omitted too. When signing a
message, the signatures on contained assertions, shards, and zones must be
omitted.
Add subject zone and context to contained shards and assertions if not
present, inheriting them from their containing shard or zone.
Create a stub signature within an array within a signatures (0) key at the
appropriate place in the object, containing the algorithm ID, timestamps
and hash chain token, if present, but a null value in the place of the
signature content.
Normalize the serialized object by emitting all keys in CBOR maps in
ascending numerical order. Note that when serializing anything with a
Content array, the order of the content array is preserved.
If the serialized object is a Message, it should be tagged with the RAINS
tag.
Generate a signature on the resulting byte stream according to the algorithm
selected.
Add the full signature to the signatures array at the appropriate point in
the object.
To verify a signature, generate the byte stream as for signing, then verify
the signature according to the algorithm selected.
The following algorithms are supported:
Code
Signatures
Hash/HMAC
Format
1
ed25519
sha-512
See
2
ed448
shake256
See
3
ecdsa-256
sha-256
See
4
ecdsa-384
sha-384
See
EdDSA public keys consist of a single value, a 32-byte bit string generated as
in Section 5.1.5 of for Ed25519, and a 57-byte bit string
generated as in Section 5.2.5 of for Ed448. The third element in a
RAINS delegation object is this bit string encoded as a CBOR byte array. RAINS
delegation objects for Ed25519 keys are therefore represented by the array [5,
1, k]; and for Ed448 keys as [5, 2, k].
Ed25519 and Ed448 signatures are are a combination of two non-negative
integers, called “R” and “S” in sections 5.1.6 and 5.2.6, respectively, of
. An Ed25519 signature is represented as a 64-byte array containing
the the concatenation of R and S, and an Ed448 signature is represented as a
114-byte array containing the concatenation of R and S. RAINS signatures using
Ed25519 are therefore the array [1, valid-from, valid-until, R|S]; using Ed448
the array [2, valid-from, valid-until, R|S].
Ed25519 keys are generated as in Section 5.1.5 of , and Ed448 keys
as in Section 5.2.5 of . Ed25519 signatures are generated from a
normalized serialized CBOR object as in Section 5.1.6 of , and
Ed448 signatures as in section 5.2.6 of .
RAINS Server and Client implementations MUST support Ed25519 signatures for
delegation.
ECDSA public keys consist of a single value, called “Q” in . Q
is a simple bit string that represents the uncompressed form of a curve point,
concatenated together as “x | y”. The third element in a RAINS delegation
object is the Q bit string encoded as a CBOR byte array. RAINS delegation
objects for ECDSA-256 public keys are therefore represented as the array
[5, 3, Q]; and for ECDSA-384 public keys as [5, 4, Q].
ECDSA signatures are a combination of two non-negative integers, called “r”
and “s” in . A Signature using ECDSA is represented using a
four-element CBOR array, with the fourth element being “r | s” such that r is
represented as a byte array as described in Section C.2 of , and
s represented as a byte array as described in Section C.2 of .
For ECDSA-256 signatures, each integer MUST be represented as a 32-byte array.
For ECDSA-384 signatures, each integer MUST be represented as a 48-byte array.
RAINS signatures using ECDSA-256 are therefore the array [3, valid-from,
valid-until, r|s]; and for ECDSA-384 the array [4, valid-from, valid-until,
r|s].
ECDSA-256 signatures and public keys use the P-256 curve as defined in .
ECDSA-384 signatures and public keys use the P-384 curve as defined in .
ECDSA-256 and ECDSA-384 support are primarily meant for compatibility with and migration from existing DNSSEC deployments; see .
When a RAINS server or client sends the first message in a stream to a peer,
it MAY expose optional capabilities to its peer using the capabilities (1)
key. This key contains either:
an array of uniform resource names specifying capabilities supported by the
sending server, taken from the table below, with each name encoded as a
UTF-8 string.
a SHA-256 hash of the CBOR byte stream derived from normalizing such an
array by sorting it in lexicographically increasing order, then serializing
it.
This mechanism is inspired by , and is intended to be used to
reduce the overhead in exposing common sets of capabilities. Each RAINS server
can cache a set of recently-seen or common hashes, and only request the full
URN set (using notification code 399) on a cache miss.
The following URNs are presently defined; other URNs will specify future
optional features, support for alternate transport protocols and new signature
algorithms, etc.
URN
Meaning
urn:x-rains:tlssrv
Listens for connections on TLS over TCP from other RAINS servers.
Since there are only two defined capabilities at this time, RAINS servers can
be implemented with two hard-coded hashes to determine whether a peer is
listening or not. The hash presented by a server supporting urn:x-rains:tlssrv
is e5365a09be554ae55b855f15264dbc837b04f5831daeb321359e18cdabab5745; the hash
presented by a server supporting no capabilities is
76be8b528d0075f7aae98d6fa57a6d3c83ae480a8469e668d7b0af968995ac71.
A RAINS server MUST NOT assume that a peer server supports a given capability
unless it has received a message containing that capability from that server.
An exception are the capabilities indicating that a server listens for
connections using a given transport protocol; servers and clients can also
learn this information from RAINS itself (given a redirection assertion for a
named zone) or from external configuration values.
As noted in , RAINS is a message-exchange protocol that uses CBOR
as its framing. Since CBOR is self-framing – a CBOR parser can
determine when a CBOR object is complete at the point at which it has read its
final byte – RAINS requires no external framing. It can therefore run over
any streaming, multistreaming, or message-oriented transport protocol. In
order to protect query confidentiality, and support rapid deployment over a
ubiquitously implemented transport, RAINS is defined in this document to run
over persistent TLS 1.2 connections over TCP with
mutual authentication between servers, and authentication of servers by
clients. The TLS certificates of RAINS server peers can be verified as
specified in the cert-info assertions for those servers.
RAINS servers MUST support this transport; future transports can be negotiated
using the capabilities mechanism after bootstrapping using TLS 1.2. As RAINS
is an experimental protocol, RAINS servers listen on port 1022 for
connections from other RAINS servers and clients. RAINS servers should strive
to keep connections open to peer servers, unless it is clear that no future
messages will be exchanged with those peers, or in the face of resource
limitations at either peer. If a RAINS server needs to send a message to
another RAINS server to which it does not have an open connection, it attempts
to open a connection with that server.
This section describes the operation of the protocol as used among RAINS
servers. A simplified version of the protocol for client access is described
in .
Once a transport is established, any server may validly send a message with
any content to any other server. A client may send messages containing queries
to servers, and a server may sent messages containing anything other than
queries to clients.
Upon receipt of a message, a server or client parses it, and:
notes the token on the message. This token MUST be present on any
messages sent in reply to this message.
processes any capabilities present, replacing the set of capabilities known
for the peer with the set present in the message. If the present
capabilities are represented by a hash that the server does not have in its
cache, it prepares a notification of type 399 “Capability hash not
understood” to send to its peer.
splits the contents into its constituent message sections, processing them
independently.
On receipt of an assertion, shard, or zone message section, a server:
verifies its consistency (see ). If the
section is not consistent, it prepares to send a notification of type 403
Inconsistent Message to the peer, and discards the section. Otherwise, it:
determines whether it answers an outstanding query; if so, it prepares to
forward the section to the server that issued the query.
determines whether it is likely to answer a future query, according to its
configuration, policy, and query history; if so, it caches the section.
On receipt of an assertion, shard, or zone message section, a client:
determines whether it answers an outstanding query; if so, it considers the query answered. It then:
determines whether it is likely to answer a future query, according to its
configuration, policy, and query history; if so, it caches the section.
On receipt of a query, a server:
determines whether it has expired by checking the query-expires value.
If so, it drops the query silently. If not, it:
determines whether it has a stored assertion, shard, and/or zone message
section which answers the query. If so, it prepares to return the most
specific such section with the signature of the longest remaining validity to the
peer that issued the query. If not, it:
checks to see whether the query specifies option 4 (cached answers only). If
so, and if option 5 (expired assertions acceptable) is also specified, it
then checks to see if it has any cached sections that answer the query on
which signatures are expired; otherwise, processing stops. If the query does
not specify option 4, delegation proceeds as follows: the server:
determines whether it has other non-authoritative servers it can forward the
query to, according to its configuration and policy, and in compliance with
any query options (see ). If so, it prepares to forward the
query to those servers, noting the reply for the received query depends on
the replies for the forwarded query. If not, it:
determines the responsible authority servers for the zone containing the
query name in the query for the context requested, and forwards the query to
those authority servers, noting the reply for the received query depends on
the reply for the forwarded query.
If query delegation fails to return an answer within a configured timeout for
a delegated query, the server prepares to send a 504 No assertion available
response to the peer from which it received the query.
When a server creates a new query to forward to another server in response to
a query it received, it SHOULD NOT use the same token on the delegated query
as on the received query, unless option 6 Enable Tracing is present in the
received, in which case it MUST use the same token. The Enable Tracing option
is designed to allow debugging of query processing across multiple servers, It
SHOULD only be enabled by clients designed explicitly for debugging RAINS
itself, and MUST NOT be enabled by default by client resolvers.
When a server creates a new query to forward to another server in response to
a query it received, and the received query contains a query-expires time, the
delegated query MUST contain the same query-expires time. If the received
query contains no query-expires time, the delegated query MAY contain a query-
expires time of the server’s choosing, according to its configuration.
On receipt of a notification, a server’s behavior depends on the notification type:
For type 100 “Connection Heartbeat”, the server does nothing: these null
messages are used to keep long-lived connections open in the presence of
network behaviors that may drop state for idle connections.
For type 399 “Capability hash not understood”, the server prepares to send a
full capabilities list on the next message it sends to the peer.
For type 504 “No assertion available”, the server checks the token on the
message, and prepares to forward the assertion to the associated query.
For type 413 “Message too large” the server notes that large messages may
not be sent to a peer and tries again (see ), or logs
the error along with the note-data content.
For type 400 “Malformed message”, type 403 “Inconsistent message”, type 500
“Server error”, or type 501 “Server not capable”, the server logs the error
along with the note-data content, as these notifications generally represent
implementation or configuration error conditions which will require human
intervention to mitigate.
On receipt of a notification, a client’s behavior depends on the notification type:
For type 100 “Connection Heartbeat”, the client does nothing, as above.
For type 399 “Capability hash not understood”, the client prepares to send a
full capabilities list on the next message it sends to the peer.
For type 404 “No assertion exists”, the client takes the query to be
unanswerable. It may reissue the query with query option 7 to do the
verification of nonexistence again, if the server from which it received the
notification is untrusted.
For type 413 “Message too large” the client notes that large messages may
not be sent to a peer and tries again (see ), or logs
the error along with the note-data content.
For type 400 “Malformed message”, type 403 “Inconsistent message”, type 500
“Server error”, or type 501 “Server not capable”, the client logs the error
along with the note-data content, as these notifications generally represent
implementation or configuration error conditions which will require human
intervention to mitigate.
The first message a server or client sends to a peer after a new connection is
established SHOULD contain a capabilities section, if the server or client
supports any optional capabilities. See .
If the server is configured to keep long-running connections open, due to the
presence of network behaviors that may drop state for idle connections, it
SHOULD send a message containing a type 100 Connection Heartbeat notification
after a configured idle time without any messages containing other content
being sent.
As noted in many messages are sent in reply to messages
received from peers. Servers may also originate messages on their own, based
on their configuration and policy:
Proactive queries to retrieve assertions, shards, and zones for which all
signatures have expired or will soon expire, for cache management purposes.
Proactive push of assertions, shards, and zones to other servers, based on
query history or other information indicating those servers may query for
the assertions they contain.
RAINS servers MUST accept messages up to 65536 bytes in length, but MAY accept
messages of greater length, subject to resource limitations of the server. A
server with resource limitations MUST respond to a message rejected due to
length restrictions with a notification of type 413 (Message Too Large). A
server that receives a type 413 notification must note that the peer sending
the message only accepts messages smaller than the largest message it’s
successfully sent that peer, or cap messages to that peer to 65536 bytes in
length.
Since a bare assertion with a single ECDSA signature requires on the order of
180 bytes, it is clear that many full zones won’t fit into a single minimum
maximum-size message. Authorities are therefore encouraged to publish zones
grouped into shards that will fit into 65536-byte messages, to allow servers
to reply using these shards when full-zone transfers are not possible due to
message size limitations.
The data model used by the RAINS protocol allows inconsistent information to
be asserted, all resulting from misconfigured or misbehaving authority
servers. The following types of inconsistency are possible:
A lexically complete shard may omit an assertion within its shard-range
which is valid at the same time as the shard.
A zone may omit an assertion within its zone which is valid at the same time
as the zone.
An assertion prohibited by its zone’s nameset may be valid at the same time
as the zone’s nameset assertion.
RAINS relies on runtime consistency checking to mitigate inconsistency: each
server receiving an assertion, shard, or zone SHOULD, subject to resource
constraints, ensure that it is consistent with other information it has, and
if not, discard all assertions, shards, and zones in its cache, log the error,
and send a 403 Inconsistent Message to the source of the message.
Assertions are not valid unless they contain at least one signature that can
be verified from the chain of authorities specified by the name and context on
the assertion; integrity protection is built into the information model. The
infrastructure key object type allows keys to be associated with RAINS
servers in addition to zone authorities, which allows a client to
delegate integrity verification of assertions to a trusted query service (see
).
Since the job of an Internet naming service is to provide publicly-available
information mapping names to information needed to connect to the services
they name, confidentiality protection for assertions is not a goal of the
system. Specifically, the information model and the mechanism for proving
non-existence of an assertion is not designed to provide resistance against
zone enumeration.
On the other hand, confidentiality protection of query information in crucial.
Linking naming queries to a specific user can be nearly as useful to build a
profile of that user for surveillance purposes as full access to the clear
text of that client’s communications . In this revision, RAINS uses
TLS to protect communications between servers and between servers and clients,
with certificate information for RAINS infrastructure stored in RAINS itself.
Together with hop-by-hop confidentiality protection, query options, proactive
caching, default use of non-persistent tokens, and redirection among servers
can be used to mix queries and reduce the linkability of query information to
specific clients.
The protocol used by clients to issue queries to and receive responses from an
query service is a subset of the full RAINS protocol, with the following
differences:
Clients only process assertion, shard, zone, and notification sections;
sending a query to a client results in a 400 Malformed Message notification.
Clients never listen for connections; a client must initiate and maintain a
transport session to the query server(s) it uses for name resolution.
Servers only process query and notification sections when connected to
clients; a client sending assertions to a server results in a 400 Malformed
Message notification.
Since signature verification is resource-intensive, clients delegate signature
verification to query servers by default. The query server signs the message
containing results for a query using its own key (published as an infrakey
object associated with the query server’s name), and a validity time
corresponding to the signature it verified with the longest lifetime,
stripping other signatures from the reply. This behavior can be disabled by a
client by specifying query option 7, allowing the client to do its own
verification.
The following subsections discuss issues that must be considered in any
deployment of RAINS at scale.
An assertion can contain multiple signatures, each with a different lifetime.
Signature lifetimes are equivalent to a time to live in the present DNS:
authorities should compute a new signature for each validity period, and make
these new signatures available when old ones are expiring.
Since assertion lifetime management is based on a real-time clock expressed in
UTC, RAINS servers MUST use a clock synchronization protocol such as NTP
.
The secret keys associated with public keys for each RAINS server (via
infrakey objects) must be available on that server, whether through a hardware
or software security device, so they can sign messages on demand; this is
particularly important for query servers. In addition, the secret keys
associated with TLS certificates for each server (published via certinfo
objects) must be available as well in order to establish TLS sessions.
However, storing zone secret keys (associated via delegation objects) on RAINS
servers would represent a more serious operational risk. To keep this from
being necessary, authority servers have an additional signer interface, from
which they will accept and cache any assertion, shard, or zone for which they
are authority servers until at least the end of validity of the last
signature, provided the signature is verifiable.
Although RAINS supports Shards and Zones containing unsigned assertions,
protecting the integrity of those Assertions by the signature on the Shard or
Zone, it is RECOMMENDED that authorities sign each Assertion, even those
contained within a Shard or Zone, in order to minimize the size of positive
answers to queries.
A client that will not do its own verification must be able to discover the
query server(s) it should trust for resolution. Integration with DHCP is left
to a future revision of this document.
In any case, clients MUST provide a configuration interface to allow a user to
specify (by address or name) and/or constrain (by certificate property) a
preferred/trusted query server. This would allow client on an untrusted network to
use an untrusted locally-available query server to discover a preferred query server
(doing key verification on its own for bootstrapping), before connecting to
that query server for normal name resolution.
Full adoption of RAINS would require changes to every client device (replacing
DNS stub resolvers with RAINS clients) and name server on the Internet. In
addition, most client software would need to change, as well, to get the full
benefits of explicit context in name resolution. This is an unrealistic goal.
RAINS servers can, however, coexist with Domain Name System servers and
clients during an indefinite transition period. RAINS assertions can be
algorithmically translated into DNS answers, and RAINS queries can be
algorithmically translated into DNS queries, by RAINS to DNS gateways, given
the mostly compatible information models used by the two.
While DNSSEC and RAINS keys for equivalent ciphersuites are compatible with
each other, there is no equivalent to query option 7 for gateways, since the
RAINS signatures are generated over the RAINS bytestream for an assertion, not
the DNS bytestream. Therefore, RAINS to DNS gateways must provide verification
services for DNS clients. DNS over TLS SHOULD be used between the
DNS client and gateway to ensure confidentiality and integrity for queries and
answers.
Object type mappings are as follows:
Objects of type name can (largely) be represented as CNAME RRs.
Objects of type ip6-addr can be represented as AAAA RRs.
Objects of type ip4-addr can be represented as A RRs.
Objects of type redirection can be represented as NS RRs.
Objects of type cert-info can be represented as TLSA RRs
Objects of type service-info can be represented as SRV RRs.
There are a few object types without mappings:
Objects of type delegation can be represented as DS RRs, and signatures as
RRSIG RRs, but since these keys are verified by the gateway, there is no need
to represent this information to the client.
Objects of type infrakey cannot be represented in DNS, but are irrelevant for
DNS translation of RAINS messages, since DNS does not support server signing
of responses.
Objects of type registrar and registrant cannot be represented in DNS; clients
can use WHOIS instead. In addition, RRTYPEs could be added for them in the
future if RAINS sees significant deployment with DNS as a front-end protocol.
Objects of type nameset cannot be represented in DNS; the current equivalent
are the IDNA parameters maintained by IANA (for the DNS root zone only) at
https://www.iana.org/assignments/idna-tables-6.3.0/idna-tables-6.3.0.xhtml.
When translating a DNS query from a client to a RAINS query for that client,
client options can be set on a per-server, per-client, or per-query basis
using some out of band configuration options.
When translating a RAINS assertion to a DNS answer, the gateway can use the
time to expiry for the verified signature as the TTL.
There is no method for exposing context information in a DNS query or answer.
Therefore, queries and answers at a RAINS gateway are only supported for the
global context “.”.
The protocol described in this document is intended primarily as a prototype
for discussion, though the goal of the document is to specify RAINS completely
enough to allow independent, interoperable implementation of clients an
servers. The massive inertia behind the deployment of the present domain name
system makes full deployment as a replacement for DNS unlikely. Despite this,
there are some criteria by which the success of the RAINS experiment may be
judged:
First, deployment in simulated or closed networks, or in alternate Internet
architectures such as SCION, allows implementation experience with the
features of RAINS which DNS lacks (signatures as a first-order delegation
primitive, support for explicit contexts, explicit tradeoffs in queries,
runtime availability of registrar/registrant data, and nameset support),
which in turn may inform the specification and deployment of these features
on the present DNS.
Second, deployment of RAINS “islands” in the present Internet alongside DNS on
a per-domain basis would allow for comparison between operational and
implementation complexity and efficiency and benefits derived from RAINS’
features, as information for future development of the DNS protocol.
The present revision of this document has no actions for IANA.
The authors have registered the CBOR tag 15309736 to identify RAINS messages
in the CBOR tag registry at
https://www.iana.org/assignments/cbor-tags/cbor-tags.xhtml.
RAINS servers currently listen for connections from other servers on Port
1022. Future revisions of this document may specify a different port,
registered with IANA via Expert Review .
The symbol table in this document in , the notification code
table in , and the signature algorithm table in
may be candidates for IANA registries in future revisions
of this document.
The urn:x-rains namespace used by the RAINS capability mechanism in
may be a candidate for replacement with an IANA-registered
namespace in a future revision of this document.
This document specifies a new, experimental protocol for Internet name
resolution, with mandatory integrity protection for assertions about names
built into the information model, and confidentiality for query information
protected on a hop-by-hop basis. See especially ,
, ,
, and for security-relevant
details.
Thanks to Daniele Asoni, Laurent Chuat, Markus Deshon, Christian Fehlmann, Ted
Hardie, Joe Hildebrand, Tobias Klausmann, Steve Matsumoto, Adrian Perrig,
Raphael Reischuk, Stephen Shirley, Andrew Sullivan, and Suzanne Woolf for the
discussions leading to the design of this protocol.
Properties of an Ideal Naming Service
This document specifies a set of necessary functions and desirable properties of an ideal system for resolving names to addresses and associated information for establishing communication associations in the Internet. For each property, it briefly explains the rationale behind it, and how the property is or could be met with the present Domain Name System. It is intended to start a discussion within the IAB's Names and Identifiers program about gaps between the present reality of DNS and the naming service the Internet needs by returning to first principles.
Transmission Control Protocol
Address Allocation for Private Internets
This document describes address allocation for private internets. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.
Key words for use in RFCs to Indicate Requirement Levels
In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.
A DNS RR for specifying the location of services (DNS SRV)
This document describes a DNS RR which specifies the location of the server(s) for a specific protocol and domain. [STANDARDS-TRACK]
UTF-8, a transformation format of ISO 10646
ISO/IEC 10646-1 defines a large character set called the Universal Character Set (UCS) which encompasses most of the world's writing systems. The originally proposed encodings of the UCS, however, were not compatible with many current applications and protocols, and this has led to the development of UTF-8, the object of this memo. UTF-8 has the characteristic of preserving the full US-ASCII range, providing compatibility with file systems, parsers and other software that rely on US-ASCII values but are transparent to other values. This memo obsoletes and replaces RFC 2279.
Unique Local IPv6 Unicast Addresses
This document defines an IPv6 unicast address format that is globally unique and is intended for local communications, usually inside of a site. These addresses are not expected to be routable on the global Internet. [STANDARDS-TRACK]
Experimental Values In IPv4, IPv6, ICMPv4, ICMPv6, UDP, and TCP Headers
When experimenting with or extending protocols, it is often necessary to use some sort of protocol number or constant in order to actually test or experiment with the new function, even when testing in a closed environment. This document reserves some ranges of numbers for experimentation purposes in specific protocols where the need to support experimentation has been identified, and it describes the numbers that have already been reserved by other documents. [STANDARDS-TRACK]
The Transport Layer Security (TLS) Protocol Version 1.2
This document specifies Version 1.2 of the Transport Layer Security (TLS) protocol. The TLS protocol provides communications security over the Internet. The protocol allows client/server applications to communicate in a way that is designed to prevent eavesdropping, tampering, or message forgery. [STANDARDS-TRACK]
Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile
This memo profiles the X.509 v3 certificate and X.509 v2 certificate revocation list (CRL) for use in the Internet. An overview of this approach and model is provided as an introduction. The X.509 v3 certificate format is described in detail, with additional information regarding the format and semantics of Internet name forms. Standard certificate extensions are described and two Internet-specific extensions are defined. A set of required certificate extensions is specified. The X.509 v2 CRL format is described in detail along with standard and Internet-specific extensions. An algorithm for X.509 certification path validation is described. An ASN.1 module and examples are provided in the appendices. [STANDARDS-TRACK]
Concise Binary Object Representation (CBOR)
The Concise Binary Object Representation (CBOR) is a data format whose design goals include the possibility of extremely small code size, fairly small message size, and extensibility without the need for version negotiation. These design goals make it different from earlier binary serializations such as ASN.1 and MessagePack.
Digital Signature Standard FIPS 186-3
Edwards-Curve Digital Signature Algorithm (EdDSA)
This document describes elliptic curve signature scheme Edwards-curve Digital Signature Algorithm (EdDSA). The algorithm is instantiated with recommended parameters for the edwards25519 and edwards448 curves. An example implementation and test vectors are provided.
Domain names - implementation and specification
This RFC is the revised specification of the protocol and format used in the implementation of the Domain Name System. It obsoletes RFC-883. This memo documents the details of the domain name client - server communication.
IP Version 6 Addressing Architecture
This specification defines the addressing architecture of the IP Version 6 (IPv6) protocol. The document includes the IPv6 addressing model, text representations of IPv6 addresses, definition of IPv6 unicast addresses, anycast addresses, and multicast addresses, and an IPv6 node's required addresses.This document obsoletes RFC 3513, "IP Version 6 Addressing Architecture". [STANDARDS-TRACK]
Classless Inter-domain Routing (CIDR): The Internet Address Assignment and Aggregation Plan
This memo discusses the strategy for address assignment of the existing 32-bit IPv4 address space with a view toward conserving the address space and limiting the growth rate of global routing state. This document obsoletes the original Classless Inter-domain Routing (CIDR) spec in RFC 1519, with changes made both to clarify the concepts it introduced and, after more than twelve years, to update the Internet community on the results of deploying the technology described. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.
Guidelines for Writing an IANA Considerations Section in RFCs
Many protocols make use of identifiers consisting of constants and other well-known values. Even after a protocol has been defined and deployment has begun, new values may need to be assigned (e.g., for a new option type in DHCP, or a new encryption or authentication transform for IPsec). To ensure that such quantities have consistent values and interpretations across all implementations, their assignment must be administered by a central authority. For IETF protocols, that role is provided by the Internet Assigned Numbers Authority (IANA).In order for IANA to manage a given namespace prudently, it needs guidelines describing the conditions under which new values can be assigned or when modifications to existing values can be made. If IANA is expected to play a role in the management of a namespace, IANA must be given clear and concise instructions describing that role. This document discusses issues that should be considered in formulating a policy for assigning values to a namespace and provides guidelines for authors on the specific text that must be included in documents that place demands on IANA.This document obsoletes RFC 2434. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.
Network Time Protocol Version 4: Protocol and Algorithms Specification
The Network Time Protocol (NTP) is widely used to synchronize computer clocks in the Internet. This document describes NTP version 4 (NTPv4), which is backwards compatible with NTP version 3 (NTPv3), described in RFC 1305, as well as previous versions of the protocol. NTPv4 includes a modified protocol header to accommodate the Internet Protocol version 6 address family. NTPv4 includes fundamental improvements in the mitigation and discipline algorithms that extend the potential accuracy to the tens of microseconds with modern workstations and fast LANs. It includes a dynamic server discovery scheme, so that in many cases, specific server configuration is not required. It corrects certain errors in the NTPv3 design and implementation and includes an optional extension mechanism. [STANDARDS-TRACK]
Elliptic Curve Digital Signature Algorithm (DSA) for DNSSEC
This document describes how to specify Elliptic Curve Digital Signature Algorithm (DSA) keys and signatures in DNS Security (DNSSEC). It lists curves of different sizes and uses the SHA-2 family of hashes for signatures. [STANDARDS-TRACK]
The DNS-Based Authentication of Named Entities (DANE) Transport Layer Security (TLS) Protocol: TLSA
Encrypted communication on the Internet often uses Transport Layer Security (TLS), which depends on third parties to certify the keys used. This document improves on that situation by enabling the administrators of domain names to specify the keys used in that domain's TLS servers. This requires matching improvements in TLS client software, but no change in TLS server software. [STANDARDS-TRACK]
Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content
The Hypertext Transfer Protocol (HTTP) is a stateless \%application- level protocol for distributed, collaborative, hypertext information systems. This document defines the semantics of HTTP/1.1 messages, as expressed by request methods, request header fields, response status codes, and response header fields, along with the payload of messages (metadata and body content) and mechanisms for content negotiation.
Confidentiality in the Face of Pervasive Surveillance: A Threat Model and Problem Statement
Since the initial revelations of pervasive surveillance in 2013, several classes of attacks on Internet communications have been discovered. In this document, we develop a threat model that describes these attacks on Internet confidentiality. We assume an attacker that is interested in undetected, indiscriminate eavesdropping. The threat model is based on published, verified attacks.
Guidelines for Cryptographic Algorithm Agility and Selecting Mandatory-to-Implement Algorithms
Many IETF protocols use cryptographic algorithms to provide confidentiality, integrity, authentication, or digital signature. Communicating peers must support a common set of cryptographic algorithms for these mechanisms to work properly. This memo provides guidelines to ensure that protocols have the ability to migrate from one mandatory-to-implement algorithm suite to another over time.
Specification for DNS over Transport Layer Security (TLS)
This document describes the use of Transport Layer Security (TLS) to provide privacy for DNS. Encryption provided by TLS eliminates opportunities for eavesdropping and on-path tampering with DNS queries in the network, such as discussed in RFC 7626. In addition, this document specifies two usage profiles for DNS over TLS and provides advice on performance considerations to minimize overhead from using TCP and TLS with DNS.This document focuses on securing stub-to-recursive traffic, as per the charter of the DPRIVE Working Group. It does not prevent future applications of the protocol to recursive-to-authoritative traffic.
Client Subnet in DNS Queries
This document describes an Extension Mechanisms for DNS (EDNS0) option that is in active use to carry information about the network that originated a DNS query and the network for which the subsequent response can be cached. Since it has some known operational and privacy shortcomings, a revision will be worked through the IETF for improvement.
XEP-0115 Entity Capababilities
SCION Five Years Later - Revisiting Scalability, Control, and Isolation Next-Generation Networks (arXiv:1508.01651v1)
The Bugs We Have To Kill (USENIX login)
The following features were suggested during the design of RAINS, but have
been left out of the current revision of the specification to allow additional
experimentation with them before they are completely specified.
RAINS assertions are scoped in temporal validity by the lifetimes on their
signatures. This is operationally equivalent to TTL in the current DNS. An
assertion which becomes invalid can simply not be renewed by its authority.
However, very dynamic infrastructures may require impractical numbers of
signatures, and could benefit from longer validity times. Allowing an
assertion to be revoked would make this possible.
Hash-chain based revocation allows a signature (and the Assertion, Shard, or
Zone it protects) to be replaced before it expires. To use hash-chain based
revocation, a signing entity generates a hash chain from a known seed using
the hash function specified by the signature algorithm in use, and places the
Nth value derived therefrom in the hash chain revocation token on a signature.
When used, this token appears as a byte array after the signature data in the
signature array.
A revocation can be issued by generating a new section and signing it,
revealing the N-1st value from the hash chain in the revocation token. To
allow a recipient of a revoked section to verify the revocation, the following
restrictions on what can replace what apply:
An Assertion can only be replaced by another Assertion with the same
Subject within the same Context and Zone, containing an Objects array
of the same length containing the same types of Objects. To delete Object
values, those values can be replaced with Null in the replacing Assertion.
A Shard can only be replaced by another Shard with an identical shard-range
key, within the same Context and Zone. Incomplete Shards cannot be replaced.
A Zone can only be replaced by another Zone with an identical name within
the same Context.
Two codepoints have been reserved to support experimentation with this mechanism, as shown in .
Code
Signatures
Hash/HMAC
Format
Revocation
24
ecdsa-256
sha-256
See
hash-chain
25
ecdsa-384
sha-384
See
hash-chain
The main open question for experimentation is how to ensure that a revocation
is properly propagated through a RAINS infrastructure; this may require
protocol changes to work reliably.
To support this experiment, a server must additionally evaluate an assertion
it receives to determine whether it replaces any information presently in its
cache. If so, it discards the old information, and caches the new section.
A method for clients to discover local oracles needs to be specified.
Consider making negative answers less expensive by allowing a hash of a
shard with a negative answer proof to be sent back, and checked with a “no
hashed negative answers” query option. This would increase complexity
somewhat, because it would require the (re-)addition of an Answer section,
which could contain such a beast.
Consider adding semantics to note-data for automated reaction to an error.
Specifically, notification codes 400, 403, and 413 could use additional data.