Mobile Ad hoc Networking (MANET)                              U. Herberg
Internet-Draft                                                T. Clausen
Intended status: Standards Track                LIX, Ecole Polytechnique
Expires: September 30, 2011                               March 29, January 12, 2012                                  July 11, 2011

             MANET Cryptographical Signature TLV Definition
                    draft-ietf-manet-packetbb-sec-03
                    draft-ietf-manet-packetbb-sec-04

Abstract

   This document describes general and flexible TLVs (type-length-value
   structure) for representing cryptographic signatures as well as
   timestamps, using the generalized MANET packet/message format
   [RFC5444].  It defines two Packet TLVs, two Message TLVs, and two
   Address Block TLVs, for affixing cryptographic signatures and
   timestamps to a packet, message and address, respectively.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 30, 2011. January 12, 2012.

Copyright Notice

   Copyright (c) 2011 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Applicability Statement  . . . . . . . . . . . . . . . . . . .  3
   4.  Security Architecture  . . . . . . . . . . . . . . . . . . . .  4
   5.  Protocol Overview and Functioning  . . . . . . . . . . . . . .  5
   6.  Imported TLV Fields  . . . . . . . . . . . . . . . . . . . . .  5
   7.  General Signature TLV Structure  . . . . . . . . . . . . . . .  5
     7.1.  Rationale  . . . . . . . . . . . . . . . . . . . . . . . .  6
   8.  General Timestamp TLV Structure  . . . . . . . . . . . . . . .  6
   9.  Packet TLVs  . . . . . . . . . . . . . . . . . . . . . . . . .  7  6
     9.1.  Packet SIGNATURE TLV . . . . . . . . . . . . . . . . . . .  7  6
     9.2.  Packet TIMESTAMP TLV . . . . . . . . . . . . . . . . . . .  8  7
   10. Message TLVs . . . . . . . . . . . . . . . . . . . . . . . . .  8  7
     10.1. Message SIGNATURE TLV  . . . . . . . . . . . . . . . . . .  8  7
     10.2. Message TIMESTAMP TLV  . . . . . . . . . . . . . . . . . .  8  7
   11. Address Block TLVs . . . . . . . . . . . . . . . . . . . . . .  9  8
     11.1. Address Block SIGNATURE TLV  . . . . . . . . . . . . . . .  9  8
     11.2. Address Block TIMESTAMP TLV  . . . . . . . . . . . . . . .  9  8
   12. IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9  8
     12.1. TLV Registrations  . . . . . . . . . . . . . . . . . . . .  9  8
       12.1.1.  Expert Review: Evaluation Guidelines  . . . . . . . . 10  9
       12.1.2.  Packet TLV Type Registrations . . . . . . . . . . . . 10  9
       12.1.3.  Message TLV Type Registrations  . . . . . . . . . . . 10  9
       12.1.4.  Address Block TLV Type Registrations  . . . . . . . . 11 10
     12.2. New IANA Registries  . . . . . . . . . . . . . . . . . . . 11
       12.2.1.  Expert Review: Evaluation Guidelines  . . . . . . . . 12 11
       12.2.2.  Hash Function . . . . . . . . . . . . . . . . . . . . 12 11
       12.2.3.  Cryptographic Algorithm . . . . . . . . . . . . . . . 12 11
   13. Security Considerations  . . . . . . . . . . . . . . . . . . . 13 12
   14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13 12
   15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     15.1. Normative References . . . . . . . . . . . . . . . . . . . 13
     15.2. Informative References . . . . . . . . . . . . . . . . . . 14 13
   Appendix A.  Examples  Signature Decomposition into Cryptographic
                Function of a Hash Value  . . . . . . . . . . . . . . 13
     A.1.  General Signature TLV Structure  . . . . . . . . . . . . . 13
       A.1.1.   Rationale . . . . . . . . . . . . . . . . . . . . . . 14
     A.1.
     A.2.  Considerations for Calculating the Signature . . . . . . . 15
       A.2.1.   Packet SIGNATURE TLV  . . . . . . . . . . . . . . . . 15
       A.2.2.   Message SIGNATURE TLV . . . . . . . . . . . . . . . . 15
       A.2.3.   Address Block SIGNATURE TLV . . . . . . . . . . . . . 15
     A.3.  Example of a Signed Message  . . . . . . . . . . . . . . . 14 15
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16 17

1.  Introduction

   This document specifies:

   o  two TLVs for carrying cryptographic signatures and timestamps in
      packets, messages and address blocks as defined by [RFC5444],

   o  how  a generic framework for calculating cryptographic signatures are calculated, signatures,
      taking (for Message TLVs) into account the mutable message header
      fields (<msg-hop-
      limit> (<msg-hop-limit> and <msg-hop-count>) where these fields
      are present in
      messages. messages,

   o  a specific calculation of signatures, decomposed as a
      cryptographic function over the hash value of the content to be
      signed, in the Appendix A of this document.

   This document requests from IANA:

   o  allocations for these Packet, Message, and Address Block TLVs from
      the 0-223 Packet TLV range, the 0-127 Message TLV range and the
      0-127 Address Block TLV range from [RFC5444],

   o  creation of two IANA registries for recording code points for hash
      function and signature calculation, respectively.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   [RFC2119].

   This document uses the terminology and notation defined in [RFC5444].

3.  Applicability Statement

   MANET routing protocols using the format defined in [RFC5444] are
   accorded the ability to carry additional information in control
   messages and packets, through inclusion of TLVs.  Information so
   included MAY be used by a routing protocol, or by an extension of a
   routing protocol, according to its specification.

   This document specifies how to include a cryptographic signature for
   a packet, message or address by way of such TLVs.  This document also
   specifies how to treat "mutable" fields (<msg-hop-count> and <msg-
   hop-limit>), if present, in the message header when calculating
   signatures, such that the resulting signature can be correctly
   verified by any recipient, and how to include this signature.

4.  Security Architecture

   Basic MANET routing protocol specifications are often "oblivious to
   security", however have a clause allowing

   This document is split into two parts: (i) a control message generic framework of
   creating signatures in the presence of mutable fields, and how to be
   rejected
   include these signatures in TLVs, (ii) a specific description of how
   to calculate a signature, using a cryptographic function over the
   hash value of the content to be signed, in the Appendix A of this
   document.  Note that (ii) is a possible and widely-used way of
   calculating a signature, but other means may exist.  Such other means
   of calculating a signature have to be specified in another document.
   That new document MUST use the TLV structures specified in this
   document, as well as the described considerations when calculating
   the signatures.

4.  Security Architecture

   Basic MANET routing protocol specifications are often "oblivious to
   security", however have a clause allowing a control message to be
   rejected as "badly formed" prior to it being processed or forwarded.
   Protocols such as [NHDP] [RFC6130] and [OLSRv2] recognize external reasons
   (such as failure to verify a signature) for rejecting a message as
   "badly formed", and therefore "invalid for processing".  This
   architecture is a result of the observation that with respect to
   security in MANETs, "one size rarely fits all" and that MANET routing
   protocol deployment domains have varying security requirements
   ranging from "unbreakable" to "virtually none".  The virtue of this
   approach is that MANET routing protocol specifications (and
   implementations) can remain "generic", with extensions providing
   proper deployment-domain specific security mechanisms.

   The MANET routing protocol "security architecture", in which this
   specification situates itself, can therefore be summarized as
   follows:

   o  Security-oblivious MANET routing protocol specifications, with a
      clause allowing an extension to reject a message (prior to
      processing/forwarding) as "badly formed".

   o  MANET routing protocol security extensions, rejecting messages as
      "badly formed", as appropriate for a given deployment-domain
      specific security requirement.

   o  Code-points and an exchange format for information, necessary for
      specification of such MANET routing protocol security extensions.

   This document addresses the last of these issues, by specifying a
   common exchange format for cryptographic signatures, making
   reservations from within the Packet TLV, Message TLV and Address
   Block TLV registries of [RFC5444], to be used (and shared) among
   MANET routing protocol security extensions, establishing extensions.

   For the specific decomposition of a signature into a cryptographic
   function over a hash value, specified in Appendix A, this document
   establishes two IANA registries for code-points for hash functions
   and cryptographic functions adhering to [RFC5444].

   With respect to [RFC5444], this document:

   o  is intended to be used in the non-normative, but intended, mode of
      use of [RFC5444] as described in its Appendix B.

   o  is a specific example of the Security Considerations section of
      [RFC5444] (the authentication part).

5.  Protocol Overview and Functioning

   This specification does not describe a protocol, nor does it mandate
   specific router or protocol behavior.  It represents a purely
   syntactical representation of security related information for use
   with [RFC5444] addresses, messages and packets, as well as
   establishes IANA registrations and registries.

6.  Imported TLV Fields

   In this specification, the following TLV fields from [RFC5444] are
   used:

   <msg-hop-limit>  - hop limit of a message, as specified in Section
      5.2 of [RFC5444].

   <msg-hop-count>  - hop count of a message, as specified in Section
      5.2 of [RFC5444].

   <length>  - length of a TLV in octets, as specified in Section 5.4.1
      of [RFC5444].

7.  General Signature TLV Structure

   The following data structure allows a generic representation of a
   cryptographic
   signature, including specification of the appropriate hash function
   and cryptographic function used for calculating the signature.  This <signature> data structure is
   specified, using the regular expression syntax of [RFC5444], as:

             <signature> := <hash-function>
                            <cryptographic-function>
                            <key-index> <signature-value>

   where:

   <hash-function>  is an 8-bit unsigned integer field specifying

   This generic specification allows for adding a signature in a TLV,
   using TLV type extension 0, and does not stipulate how to calculate
   the
      hash function.

   <cryptographic-function>  is an 8-bit unsigned integer field
      specifying signature-value.  Appendix A specifies a concrete calculation of
   the signature-value, using a cryptographic function.

   <key-index>  is an 8-bit unsigned integer field specifying the key
      index function over a hash
   function of the key which was used content to sign the message, which allows
      unique identification be signed.  Other methods of different keys with how to
   calculate the same originator.
      It is signature-value may be specified in future documents.

8.  General Timestamp TLV Structure

   The following data structure allows the responsibility representation of each key originator to make sure that
      actively used keys that it issues have distinct key indices and
      that all key indices have a value unequal to 0x00.  Value 0x00
   timestamp.  This <timestamp> data structure is
      reserved for a pre-installed, shared key.

   <signature-value> specified as:

          <timestamp> := <time-value>

   where:

   <time-value>  is an unsigned integer field, whose length is
      <length> - 3, <length>,
      and which contains the cryptographic signature. timestamp.  The basic version value of this TLV assumes that calculating the signature
   can be decomposed into:

      signature-value = cryptographic-function(hash-function(content))

   The hash function and the cryptographic function correspond variable is
      to the
   entries in two IANA registries, set up be interpreted by this specification in
   Section 12.

7.1.  Rationale

   The rationale for separating the hash function and the cryptographic
   function into two octets instead of having all combinations in a
   single octet - possibly routing protocol as TLV specified by the type
      extension - is twofold: First, if
   further hash functions or cryptographic functions are added in the
   future, the number space might not remain continuous.  More
   importantly, the number space of possible combinations would be
   rapidly exhausted. the Timestamp TLV, see Section 12.

   A timestamp is essentially "freshness information".  As new or improved cryptographic mechanism are
   continuously being developed such, its
   setting and introduced, this format should interpretation is to be
   able determined by the routing
   protocol (or the extension to accommodate such a routing protocol) that uses it, and
   may e.g. correspond to a UNIX-timestamp, GPS timestamp or a simple
   sequence number.

9.  Packet TLVs

   Two Packet TLVs are defined, for including the foreseeable future.

   The rationale cryptographic
   signature of a packet, and for not including a field that lists parameters of the timestamp indicating the
   time at which the cryptographic signature in the was calculated.

9.1.  Packet SIGNATURE TLV

   A Packet SIGNATURE TLV is, that before being able to
   validate a cryptographic signature, routers have to exchange or
   acquire keys (e.g. public keys).  Any additional parameters can be
   provided together with the keys in that bootstrap process.  It is
   therefore not necessary, and would even entail an extra overhead, example of a Signature TLV as described
   in Section 7.

   The following considerations apply:

   o  As packets defined in [RFC5444] are never forwarded by routers, it
      is unnecessary to
   transmit consider mutable fields (e.g. <msg-hop-count>
      and <msg-hop-limit>), if present, when calculating the parameters within every message.  One inherently
   included parameter is signature.

   o  any Packet SIGNATURE TLVs already present in the length of Packet TLV block
      MUST be removed before calculating the signature, which is <length>
   - 3 and which depends on the choice of the cryptographic function.

8.  General Timestamp Packet
      TLV Structure block size MUST be recalculated accordingly.  The following data structure allows TLVs can be
      restored after having calculated the representation of a
   timestamp.  This <timestamp> data structure signature value.

   The rationale for removing any Packet SIGNATURE TLV already present
   prior to calculating the signature, is specified as:

          <timestamp> := <time-value>

   where:

   <time-value> that several signatures may be
   added to the same packet, e.g., using different signature functions.

9.2.  Packet TIMESTAMP TLV

   A Packet TIMESTAMP TLV is an unsigned integer field, whose length is <length>,
      and which example of a Timestamp TLV as described
   in Section 8.  If a packet contains a TIMESTAMP TLV and a SIGNATURE
   TLV, the timestamp.  The value of this variable is TIMESTAMP TLV SHOULD be added to the packet before any
   SIGNATURE TLV, in order that it be interpreted by included in the routing protocol as specified by calculation of the type
      extension of the Timestamp TLV, see Section 12.

   A timestamp is essentially "freshness information".  As such, its
   setting and interpretation is to be determined by the routing
   protocol (or the extension to a routing protocol) that uses it, and
   may e.g. correspond to a UNIX-timestamp, GPS timestamp or a simple
   sequence number.

9.  Packet
   signature.

10.  Message TLVs

   Two Packet Message TLVs are defined, for including the cryptographic
   signature of a packet, message, and for including the timestamp indicating
   the time at which the cryptographic signature was calculated.

9.1.  Packet

10.1.  Message SIGNATURE TLV

   A Packet Message SIGNATURE TLV is an example of a Signature TLV as described
   in Section 7.  When calculating determining the <signature-value> for a Packet,
   the signature is calculated over the three fields <hash-function>,
   <cryptographic-function> and <key-index> (in that order),
   concatenated with the entire Packet, including message,
   the packet header, all
   Packet TLVs (other than Packet SIGNATURE TLVs) and all included
   Messages and their message headers.

   The following considerations apply: must be applied:

   o  As packets defined in [RFC5444] are never forwarded by routers, it
      is unnecessary to consider mutable  the fields (e.g. <msg-hop-count> <msg-hop-limit> and <msg-hop-limit>), <msg-hop-count>, if present, MUST
      both be assumed to have the value 0 (zero) when calculating the
      signature.

   o  any Packet Message SIGNATURE TLVs already present in the Packet Message TLV
      block MUST be removed before calculating the signature, and the Packet
      message size as well as the Message TLV block size MUST be
      recalculated accordingly.  The TLVs can be restored after having
      calculated the signature value.

   The rationale for removing any Packet Message SIGNATURE TLV already present
   prior to calculating the signature, is that several signatures may be
   added to the same packet, message, e.g., using different signature functions.

9.2.  Packet

10.2.  Message TIMESTAMP TLV

   A Packet Message TIMESTAMP TLV is an example of a Timestamp TLV as described
   in Section 8.  If a packet message contains a TIMESTAMP TLV and a SIGNATURE
   TLV, the TIMESTAMP TLV SHOULD be added to the packet message before any the
   SIGNATURE TLV, in order that it be included in the calculation of the
   signature.

10.  Message

11.  Address Block TLVs

   Two Message Address Block TLVs are defined, for including the associating a cryptographic
   signature of a message, to an address, and for including the timestamp indicating
   the time at which the cryptographic signature was calculated.

10.1.  Message

11.1.  Address Block SIGNATURE TLV

   A Message

   An Address Block SIGNATURE TLV is an example of a Signature TLV as
   described in Section 7.  When determining the <signature-value> for a message,
   the  The signature is calculated over the three fields <hash-function>,
   <cryptographic-function>, and <key-index> (in that order),
   concatenated with the entire message with the following
   considerations:

   o  the fields <msg-hop-limit> and <msg-hop-count>, if present, MUST
      both be assumed to have the value 0 (zero) when calculating the
      signature.

   o  any Message SIGNATURE TLVs already present in the Message TLV
      block MUST be removed before calculating the signature, and the
      message size as well as the Message TLV block size MUST be
      recalculated accordingly.  The TLVs can be restored after having
      calculated the signature value.

   The rationale for removing any Message SIGNATURE TLV already present
   prior to calculating the signature, is that several signatures may be
   added to the same message, e.g., using different signature functions.

10.2.  Message TIMESTAMP TLV

   A Message TIMESTAMP TLV is an example of a Timestamp TLV as described
   in Section 8.  If a message contains a TIMESTAMP TLV and a SIGNATURE
   TLV, the TIMESTAMP TLV SHOULD be added to the message before the
   SIGNATURE TLV, in order that it be included in the calculation of the
   signature.

11.  Address Block TLVs

   Two Address Block TLVs are defined, for associating a cryptographic
   signature to an address, and for including the timestamp indicating
   the time at which the cryptographic signature was calculated.

11.1.  Address Block SIGNATURE TLV

   An Address Block SIGNATURE TLV is an example of a Signature TLV as
   described in Section 7.  The signature is calculated over the three
   fields <hash-function>, <cryptographic-function>, and <key-index> (in
   that order), concatenated with the address,
   address, concatenated with any other values, for example, any other
   TLV value that is associated with that address.  A routing protocol
   or routing protocol extension using Address Block SIGNATURE TLVs MUST
   specify how to include any such concatenated attribute of the address
   in the verification process of the signature.

11.2.  Address Block TIMESTAMP TLV

   An Address Block TIMESTAMP TLV is an example of a Timestamp TLV as
   described in Section 8.  If both a TIMESTAMP TLV and a SIGNATURE TLV
   are associated with an address, the timestamp value should be
   considered when calculating the value of the signature.

12.  IANA Considerations

   This section specifies requests to IANA.

12.1.  TLV Registrations

   This specification defines:

   o  two Packet TLV types which must be allocated from the 0-223 range
      of the "Assigned Packet TLV Types" repository of [RFC5444] as
      specified in Table 1,

   o  two Message TLV types which must be allocated from the 0-127 range
      of the "Assigned Message TLV Types" repository of [RFC5444] as
      specified in Table 2,

   o  and two Address Block TLV types which must be allocated from the
      0-127 range of the "Assigned Address Block TLV Types" repository
      of [RFC5444] as specified in Table 3.

   This specification requests:

   o  set up of type extension registries for these TLV types.

   IANA is requested to assign the same numerical value to the Packet
   TLV, Message TLV and Address Block TLV types with the same name.

12.1.1.  Expert Review: Evaluation Guidelines

   For the registries for TLV type extensions where an Expert Review is
   required, the designated expert SHOULD take the same general
   recommendations into consideration as are specified by [RFC5444].

   For the Timestamp TLV, the same type extensions for all Packet,
   Message and Address TLVs should be numbered identically.

12.1.2.  Packet TLV Type Registrations

   The Packet TLVs as specified in Table 1 must be allocated from the
   "Packet TLV Types" namespace of [RFC5444].

   +-----------+------+-----------+------------------------------------+
   |    Name   | Type |    Type   |             Description            |
   |           |      | Extension |                                    |
   +-----------+------+-----------+------------------------------------+
   | SIGNATURE | TBD3 TBD1 |     0     |        Signature of a packet       |
   |           |      |   1-223     1     |     Signature, decomposed into     |
   |           |      |           | cryptographic function over a hash |
   |           |      |           |  value, as specified in Appendix A |
   |           |      |           |          in this document.         |
   |           |      |   2-223   |            Expert Review           |
   |           |      |  224-255  |          Experimental Use          |
   | TIMESTAMP | TBD4 TBD2 |     0     |   Unsigned timestamp of arbitrary  |
   |           |      |           |   length, given by the TLV length  |
   |           |      |           |  field. The MANET routing protocol |
   |           |      |           |   has to define how to interpret   |
   |           |      |           |           this timestamp           |
   |           |      |   1-223   |            Expert Review           |
   |           |      |  224-255  |          Experimental Use          |
   +-----------+------+-----------+------------------------------------+

                         Table 1: Packet TLV types

12.1.3.  Message TLV Type Registrations

   The Message TLVs as specified in Table 2 must be allocated from the
   "Message TLV Types" namespace of [RFC5444].

   +-----------+------+-----------+------------------------------------+
   |    Name   | Type |    Type   |             Description            |
   |           |      | Extension |                                    |
   +-----------+------+-----------+------------------------------------+
   | SIGNATURE | TBD1 TBD3 |     0     |       Signature of a message       |
   |           |      |   1-223   |            Expert Review           |     1     |     Signature, decomposed into     |
   |  224-255           |          Experimental Use      |           | TIMESTAMP cryptographic function over a hash |
   |           |      |           |  value, as specified in Appendix A |
   |           |      |           |          in this document.         |
   |           |      |   2-223   |            Expert Review           |
   | TBD2           |      |  224-255  |          Experimental Use          |
   | TIMESTAMP | TBD4 |     0     |   Unsigned timestamp of arbitrary  |
   |           |      |           |   length, given by the TLV length  |
   |           |      |           |               field.               |
   |           |      |   1-223   |            Expert Review           |
   |           |      |  224-255  |          Experimental Use          |
   +-----------+------+-----------+------------------------------------+

                        Table 2: Message TLV types

12.1.4.  Address Block TLV Type Registrations

   The Address Block TLVs as specified in Table 3 must be allocated from
   the "Address Block TLV Types" namespace of [RFC5444].

   +-----------+------+-----------+------------------------------------+
   |    Name   | Type |    Type   |             Description            |
   |           |      | Extension |                                    |
   +-----------+------+-----------+------------------------------------+
   | SIGNATURE | TBD1 TBD5 |     0     |   Signature of an object (e.g. an  |
   |           |      |           |              address)              |
   |           |      |   1-223     1     |     Signature, decomposed into     |
   |           |      |           | cryptographic function over a hash |
   |           |      |           |  value, as specified in Appendix A |
   |           |      |           |          in this document.         |
   |           |      |   2-223   |            Expert Review           |
   |           |      |  224-255  |          Experimental Use          |
   | TIMESTAMP | TBD2 TBD6 |     0     |   Unsigned timestamp of arbitrary  |
   |           |      |           |   length, given by the TLV length  |
   |           |      |           |               field.               |
   |           |      |   1-223   |            Expert Review           |
   |           |      |  224-255  |          Experimental Use          |
   +-----------+------+-----------+------------------------------------+

                     Table 3: Address Block TLV types

12.2.  New IANA Registries

   This document introduces three namespaces that have been registered:
   Packet TLV Types, Message TLV Types, and Address Block TLV Types.
   This section specifies IANA registries for these namespaces and
   provides guidance to the Internet Assigned Numbers Authority
   regarding registrations in these namespaces.

   The following terms are used with the meanings defined in [BCP26]:
   "Namespace", "Assigned Value", "Registration", "Unassigned",
   "Reserved", "Hierarchical Allocation", and "Designated Expert".

   The following policies are used with the meanings defined in [BCP26]:
   "Private Use", "Expert Review", and "Standards Action".

12.2.1.  Expert Review: Evaluation Guidelines

   For the registries for the following tables where an Expert Review is
   required, the designated expert SHOULD take the same general
   recommendations into consideration as are specified by [RFC5444].

12.2.2.  Hash Function

   IANA is requested to create a new registry for the hash functions
   that can be used when creating a signature. signature, as specified in the
   Appendix A of this document.  The initial assignments and allocation
   policies are specified in Table 4.

   +-------------+-----------+-----------------------------------------+
   |     Hash    | Algorithm |               Description               |
   |   function  |           |                                         |
   |    value    |           |                                         |
   +-------------+-----------+-----------------------------------------+
   |      0      |    none   | The "identity function": the hash value |
   |             |           |    of an object is the object itself    |
   |    1-223    |           |              Expert Review              |
   |   224-255   |           |             Experimental Use            |
   +-------------+-----------+-----------------------------------------+

                      Table 4: Hash-Function registry

12.2.3.  Cryptographic Algorithm

   IANA is requested to create a new registry for the cryptographic
   function.
   function, as specified in the Appendix A of this document.  Initial
   assignments and allocation policies are specified in Table 5.

   +----------------+-----------+--------------------------------------+
   |  Cryptographic | Algorithm |              Description             |
   | function value |           |                                      |
   +----------------+-----------+--------------------------------------+
   |        0       |    none   |  The "identity function": the value  |
   |                |           |   of an encrypted hash is the hash   |
   |                |           |                itself                |
   |      1-223     |           |             Expert Review            |
   |     224-255    |           |           Experimental Use           |
   +----------------+-----------+--------------------------------------+

                 Table 5: Cryptographic function registry

13.  Security Considerations

   This document does not specify a protocol itself.  However, it
   provides a syntactical component for cryptographic signatures of
   messages and packets as defined in [RFC5444].  It can be used to
   address security issues of a protocol or extension that uses the
   component specified in this document.  As such, it has the same
   security considerations as [RFC5444].

   In addition, a protocol that includes this component MUST specify the
   usage as well as the security that is attained by the cryptographic
   signatures of a message or a packet.

   As an example, a routing protocol that uses this component to reject
   "badly formed" messages if a control message does not contain a valid
   signature, should indicate the security assumption that if the
   signature is valid, the message is considered valid.  It also should
   indicate the security issues that are counteracted by this measure
   (e.g. link or identity spoofing) as well as the issues that are not
   counteracted (e.g. compromised keys).

14.  Acknowledgements

   The authors would like to thank Jerome Milan (Ecole Polytechnique)
   for his advice as cryptographer.  In addition, many thanks to Bo
   Berry (Cisco), Alan Cullen (BAE), Justin Dean (NRL), Christopher
   Dearlove (BAE), Paul Lambert (Marvell), and Henning Rogge (FGAN) for Henning Rogge (FGAN) for
   their constructive comments on the document.

15.  References
15.1.  Normative References

   [BCP26]    Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", RFC 5226, BCP 26,
              May 2008.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", RFC 2119, BCP 14, March 1997.

   [RFC5444]  Clausen, T., Dearlove, C., Dean, J., and C. Adjih,
              "Generalized MANET Packet/Message Format", RFC 5444,
              February 2009.

15.2.  Informative References

   [OLSRv2]   Clausen, T., Dearlove, C., and P. Jacquet, "The Optimized
              Link State Routing Protocol version 2", work in
              progress draft-ietf-manet-olsrv2-11.txt, April 2010.

   [RFC6130]  Clausen, T., Dean, J., and C. Dearlove, "MANET
              Neighborhood Discovery Protocol (NHDP)", RFC 6130,
              March 2011.

Appendix A.  Signature Decomposition into Cryptographic Function of a
             Hash Value

   This section specifies how to calculate the signature-value in a
   Signature TLV, as described in Section 7.  A common way of
   calculating a signature is applying a cryptographic function on a
   hash value of the content.  This decomposition is specified in the
   following, using a type extension of 1 in the Signature TLVs.

A.1.  General Signature TLV Structure

   The following data structure allows representation of a cryptographic
   signature, including specification of the appropriate hash function
   and cryptographic function used for calculating the signature:

             <signature> := <hash-function>
                            <cryptographic-function>
                            <key-index>
                            <signature-value>

   where:

   <hash-function>  is an 8-bit unsigned integer field specifying the
      hash function.

   <cryptographic-function>  is an 8-bit unsigned integer field
      specifying the cryptographic function.

   <key-index>  is an 8-bit unsigned integer field specifying the key
      index of the key which was used to sign the message, which allows
      unique identification of different keys with the same originator.
      It is the responsibility of each key originator to make sure that
      actively used keys that it issues have distinct key indices and
      that all key indices have a value unequal to 0x00.  Value 0x00 is
      reserved for a pre-installed, shared key.

   <signature-value>  is an unsigned integer field, whose length is
      <length> - 3, and which contains the cryptographic signature.

   The version of this TLV, specified in this section, assumes that
   calculating the signature can be decomposed into:

      signature-value = cryptographic-function(hash-function(content))

   The hash function and the cryptographic function correspond to the
   entries in two IANA registries, set up by this specification in
   Section 12.

A.1.1.  Rationale

   The rationale for separating the hash function and the cryptographic
   function into two octets instead of having all combinations in a
   single octet - possibly as TLV type extension - is twofold: First, if
   further hash functions or cryptographic functions are added in the
   future, the number space might not remain continuous.  More
   importantly, the number space of possible combinations would be
   rapidly exhausted.  As new or improved cryptographic mechanism are
   continuously being developed and introduced, this format should be
   able to accommodate such for the foreseeable future.

   The rationale for not including a field that lists parameters of the
   cryptographic signature in the TLV is, that before being able to
   validate a cryptographic signature, routers have to exchange or
   acquire keys (e.g. public keys).  Any additional parameters can be
   provided together with the keys in that bootstrap process.  It is
   therefore not necessary, and would even entail an extra overhead, to
   transmit the parameters within every message.  One inherently
   included parameter is the length of the signature, which is <length>
   - 3 and which depends on the choice of the cryptographic function.

A.2.  Considerations for Calculating the Signature

   In the following, considerations are listed, which have to be applied
   when calculating the signature for Packet, Message and Address
   SIGNATURE TLVs, respectively.

A.2.1.  Packet SIGNATURE TLV

   When determining the <signature-value> for a Packet, the signature is
   calculated over the three fields <hash-function>, <cryptographic-
   function> and <key-index> (in that order), concatenated with the
   entire Packet, including the packet header, all Packet TLVs (other
   than Packet SIGNATURE TLVs) and all included Messages and their constructive comments on
   message headers.

A.2.2.  Message SIGNATURE TLV

   When determining the document.

15.  References

15.1.  Normative References

   [BCP26]    Narten, T. <signature-value> for a message, the signature
   is calculated over the three fields <hash-function>, <cryptographic-
   function>, and H. Alvestrand, "Guidelines <key-index> (in that order), concatenated with the
   entire message.

A.2.3.  Address Block SIGNATURE TLV

   When determining the <signature-value> for Writing an
              IANA Considerations Section in RFCs", RFC 5226, BCP 26,
              May 2008.

   [RFC2119]  Bradner, S., "Key words address, the signature
   is calculated over the three fields <hash-function>, <cryptographic-
   function>, and <key-index> (in that order), concatenated with the
   address, concatenated with any other values, for use in RFCs example, any other
   TLV value that is associated with that address.  A routing protocol
   or routing protocol extension using Address Block SIGNATURE TLVs MUST
   specify how to Indicate
              Requirement Levels", RFC 2119, BCP 14, March 1997.

   [RFC5444]  Clausen, T., Dearlove, C., Dean, J., and C. Adjih,
              "Generalized MANET Packet/Message Format", RFC 5444,
              February 2009.

15.2.  Informative References

   [NHDP]     Clausen, T., Dean, J., and C. Dearlove, "MANET
              Neighborhood Discovery Protocol (NHDP)", RFC 6130,
              March 2011.

   [OLSRv2]   Clausen, T., Dearlove, C., and P. Jacquet, "The Optimized
              Link State Routing Protocol version 2", work include any such concatenated attribute of the address
   in
              progress draft-ietf-manet-olsrv2-11.txt, April 2010.

Appendix A.  Examples

A.1. the verification process of the signature.

A.3.  Example of a Signed Message

   The sample message depicted in Figure 1 is derived from the appendix
   of [RFC5444].  A SIGNATURE Message TLV has been added, with the value
   representing a 15 14 octet long signature of the whole message.  The
   type extension of the Message TLV is 1, for the specific
   decomposition of a signature into a cryptographic function over a
   hash value, as specified in Appendix A.

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 0 1 0 0 0|    Packet Sequence Number     | Message Type  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |1 1 1 1 0 0 1 1|0 0 0 0 0 0 0 0 0 1 0 0 1 1 0 0|   Orig Addr   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |           Originator Address (cont)           |   Hop Limit   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Hop Count   |    Message Sequence Number    |0 0 0 0 0 0 0 0|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 1 1 1 1 0|   SIGNATURE   |0   |1 0 0 1 0 0 0 0|0 0 0 0 0 0 0 1|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 1 0 0 1 0|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Hash Func   |  Crypto Func  |    Key Index  |  Sign. Value  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    Signature Value (cont)                            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    Signature Value (cont)                     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    Signature Value (cont)                     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    Signature Value (cont)     |   TLV Type    |0 0 0 1 0 0 0 0|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 0 0 1 1 0|                     Value                     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                 Value (cont)                  |0 0 0 0 0 0 1 0|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 1 1 0 0 0 0|0 0 0 0 0 0 1 0|              Mid              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |              Mid              | Prefix Length |0 0 0 0 0 0 0 0|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 0 0 0 0 0|0 0 0 0 0 0 1 1|1 0 0 0 0 0 0 0|0 0 0 0 0 0 1 0|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |             Head              |              Mid              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |              Mid              |              Mid              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 1|   TLV Type    |0 0 0 1 0 0 0 0|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 0 0 0 1 0|             Value             |   TLV Type    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 1 0 0 0 0 0|  Index Start  |  Index Stop   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                 Figure 1: Example message with signature

Authors' Addresses

   Ulrich Herberg
   LIX, Ecole Polytechnique
   91128 Palaiseau Cedex,
   France

   Phone: +33 1 6933 4126
   Email: ulrich@herberg.name
   URI:   http://www.herberg.name/

   Thomas Heide Clausen
   LIX, Ecole Polytechnique
   91128 Palaiseau Cedex,
   France

   Phone: +33 6 6058 9349
   Email: T.Clausen@computer.org
   URI:   http://www.thomasclausen.org/