Mobile Ad hoc Networking (MANET)                              U. Herberg
Internet-Draft                                                T. Clausen                           Fujitsu Laboratories of America
Intended status: Standards Track                              T. Clausen
Expires: March 9, 2012                          LIX, Ecole Polytechnique
Expires: January 30, 2012                                  July 29,
                                                       September 6, 2011

             MANET Cryptographical Signature TLV Definition
                    draft-ietf-manet-packetbb-sec-05
                    draft-ietf-manet-packetbb-sec-06

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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on January 30, March 9, 2012.

Copyright Notice

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

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

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

1.  Introduction

   This document specifies:

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

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

   o  a specific calculation of signatures in the Appendix A of this
      document.  The signature is decomposed into a cryptographic
      function over the hash value of the content to be signed. messages.

   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.

   Finally, this document defines, in Section 12:

   o  one common method for generating signatures as a cryptographic
      function, calculated over the hash value of the content to be
      signed.

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

   <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].

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 MANET routing protocol, or by an extension
   of a MANET routing protocol, according to its specification.

   This document specifies how to include a cryptographic signature for
   a packet, message or a message, and addresses in address blocks within a
   message, by way of such TLVs.  This document also specifies how to
   treat "mutable" fields (<msg-hop-count> fields, specifically the <msg-hop-count> and <msg-
   hop-limit>),
   hop-limit> fields, if present, 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.

   This document describes a generic framework of for creating signatures in
   the presence of mutable fields, signatures,
   and how to include these signatures in TLVs.  In the Appendix A, one Section 12, an
   example of how to calculate a
   signature method for calculating such signatures is specified, given, using a
   cryptographic function over the hash value of the content to be
   signed.

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
   MANET routing protocols such as [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 TLV, and Address
   Block TLV registries of [RFC5444], to be used (and shared) among
   MANET routing protocol security extensions.

   For the specific decomposition of a signature into a cryptographic
   function over a hash value, specified in Appendix A, Section 12, 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. B of [RFC5444].

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

5.  Protocol  Overview and Functioning

   This document specifies a syntactical representation of security
   related information for use with [RFC5444] addresses, messages messages, and
   packets, as well as establishes IANA registrations and registries.

   Moreover, this document provides guidelines how MANET routing
   protocols and MANET routing protocol extensions, using this
   specification
   specification, should treat Signature and Timestamp TLVs, and mutable
   fields in messages.  This specification, however, specification does not represent a stand-alone stand-
   alone protocol; MANET routing protocols and MANET routing protocol
   extensions, using this specification have to specification, MUST provide instructions as to
   how to handle packets, messages and addresses with associated security
   information, associated as specified in this document.

6.  Imported

   This document requests assignment of TLV Fields

   In this specification, types from the following registries
   defined for Packet, Message and Address Block TLVs in [RFC5444].

   When a TLV fields type is assigned from [RFC5444] are
   used:

   <msg-hop-limit>  - hop limit one of these registries, a message, as specified registry
   for "Type Extensions" for that TLV type is created by IANA.  This
   document utilizes these "Type Extension" registries so created, in Section
      5.2
   order to specify internal structure (and accompanying processing) of [RFC5444].

   <msg-hop-count>  - hop count
   the <value> field of a message, TLV.

   For example, and as specified defined in Section
      5.2 this document, a SIGNATURE TLV with
   Type Extension = 0 specifies that the <value> field has no pre-
   defined internal structure, but is simply a sequence of [RFC5444].

   <length>  - length octets.  A
   SIGNATURE TLV with Type Extension = 1 specifies that the <value>
   field has a pre-defined internal structure, and defines its
   interpretation (specifically, the <value> field consists of a TLV in octets, as
   cryptographic operation over a hash value, with fields indicating
   which hash function and cryptographic operation has been used,
   specified in Section 5.4.1
      of [RFC5444].

7. 12).

   Other documents may request assignments for other Type Extensions,
   and must if so specify their internal structure (if any) and
   interpretation.

6.  General Signature TLV Structure

   The following data structure, which is the value of the Signature
   TLV, allows a generic representation of a cryptographic signature.
   This <signature> data structure is specified, using the regular
   expression syntax of [RFC5444], as:

             <signature> TLV is:

             <value> := <signature-value>

   where:

   <signature-value>  is an integer a field, whose length is <length>, and of <length> octets, which contains the signature.  The value of this variable is
      information, to be interpreted by the routing protocol signature verification
      process, as specified by the type
      extension of the Signature TLV, see Section 12.

   This generic specification allows for adding a signature in a TLV,
   using TLV type extension 0, and Type Extension.

   Note that this does not stipulate how to calculate the signature-value.  Appendix A specifies a concrete calculation <signature-
   value>, nor the internal structure hereof, if any; such MUST be
   specified by way of the signature-value, using Type Extension for the SIGNATURE TLV type,
   see Section 13.  This document specifies two such type-extensions,
   for signatures without pre-defined structures, and for signatures
   constructed by way of a cryptographic function operation over a hash
   function of the content to be signed.  Other methods of how to
   calculate the signature-value may be specified in future documents.

8. hash-value.

7.  General Timestamp TLV Structure

   The following data structure, which is the value of the Timestamp
   TLV, allows the representation of a timestamp.  This <timestamp> data
   structure is specified as:

          <timestamp> TLV is:

          <value> := <time-value>

   where:

   <time-value>  is an unsigned integer field, whose of length is <length>,
      and which
      contains the timestamp.  The value of

      Note that this variable is does not stipulate how to be interpreted by calculate the routing protocol as <time-
      value>, nor the internal structure hereof, if any; such MUST be
      specified by the type
      extension way of the Timestamp TLV, Type Extension for the TIMESTAMP TLV type,
      see Section 12. 13.

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

9.

8.  Packet TLVs

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

9.1.

8.1.  Packet SIGNATURE TLV

   A Packet SIGNATURE TLV is an example of a Signature TLV as described
   in Section 7. 6.

   The following considerations apply:

   o  As packets defined in [RFC5444] are never forwarded by routers, it
      is unnecessary to consider no
      special considerations are required regarding mutable fields (e.g.
      <msg-hop-count> and <msg-hop-limit>), if present, when calculating
      the signature.

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

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

9.2.

8.2.  Packet TIMESTAMP TLV

   A Packet TIMESTAMP TLV is an example of a Timestamp TLV as described
   in Section 8. 7.  If a packet contains a TIMESTAMP TLV and a SIGNATURE
   TLV, the TIMESTAMP TLV SHOULD be added to the packet before any
   SIGNATURE TLV, in order that it be included in the calculation of the
   signature.

10.

9.  Message TLVs

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

10.1.

9.1.  Message SIGNATURE TLV

   A Message SIGNATURE TLV is an example of a Signature TLV as described
   in Section 7. 6.  When determining the <signature-value> for a message,
   the following considerations must be applied:

   o  the  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  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  Removed SIGNATURE TLVs can SHOULD be
      restored after having calculated the signature value.

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

10.2.

9.2.  Message TIMESTAMP TLV

   A Message TIMESTAMP TLV is an example of a Timestamp TLV as described
   in Section 8. 7.  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.

10.  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.

10.1.  Address Block SIGNATURE TLV

   An Address Block SIGNATURE TLV is an example of a Signature TLV as
   described in Section 7. 6.  The signature is calculated over the
   address, concatenated with any other values, for example, any other
   TLV value that is associated with that address.  A MANET routing
   protocol or MANET 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.

10.2.  Address Block TIMESTAMP TLV

   An Address Block TIMESTAMP TLV is an example of a Timestamp TLV as
   described in Section 8. 7.  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.

11.  Signature: Basic

   The basic signature proposed, represented by way of a SIGNATURE TLV Registrations
   with Type Extension = 0, is a simple bit-field containing the
   cryptographic signature.  This specification defines:

   o  two Packet TLV types which must be allocated from assumes that the 0-223 range mechanism stipulating
   how signatures are calculated and verified is established outside of
   this specification, e.g., by way of administrative configuration or
   external out-of-band signaling.  Thus, the "Assigned Packet TLV Types" repository <signature-value> for when
   using Type Extension = 0 is:

             <signature-value> := <signature-data>

   where:

   <signature-data>  is an unsigned integer field, of [RFC5444] as
      specified in Table 1,

   o  two Message TLV types length <length>,
      which must be allocated from contains the 0-127 range cryptographic signature.

12.  Signature: Cryptographic Function over a Hash Value

   One common way of the "Assigned Message TLV Types" repository calculating a signature is applying a cryptographic
   function on a hash value of [RFC5444] as the content.  This decomposition is
   specified in Table 2,

   o  and two Address Block TLV types which must be allocated from the
      0-127 range of following, using a Type Extension = 1 in the "Assigned Address Block
   Signature TLVs.

12.1.  General Signature TLV Types" repository Structure

   The following data structure allows representation of [RFC5444] as specified in Table 3.

   This a cryptographic
   signature, including specification requests:

   o  set up of type extension registries for these TLV types with
      initial values as in Table 1 to Table 3.

   IANA is requested to assign the same numerical value to the Packet
   TLV, Message TLV appropriate hash function
   and Address Block TLV types with cryptographic function used for calculating the same name.

12.1.1.  Expert Review: Evaluation Guidelines

   For signature:

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

   where:

   <hash-function>  is an 8-bit unsigned integer field specifying the registries for TLV type extensions where
      hash function.

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

   <key-index>  is
   required, an 8-bit unsigned integer field specifying the designated expert SHOULD take key
      index of the same general
   recommendations into consideration as are specified by [RFC5444].

   For key which was used to sign the Timestamp TLV, message, which allows
      unique identification of different keys with 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 originator.
      It is the
   "Packet TLV Types" namespace of [RFC5444].

   +-----------+------+-----------+------------------------------------+
   |    Name   | Type |    Type   |             Description            |
   |           |      | Extension |                                    |
   +-----------+------+-----------+------------------------------------+
   | SIGNATURE | TBD1 |     0     |        Signature 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 packet       |
   |           |      |     1     |     Signature, decomposed into     |
   |           |      |           | cryptographic function over value not equal to 0x00.  The value
      0x00 is reserved for a hash |
   |           |      |           |  value, as pre-installed, shared key.

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

   The version of this TLV, specified in Appendix A |
   |           |      |           |          in this document.         |
   |           |      |   2-223   |            Expert Review           |
   |           |      |  224-255  |          Experimental Use          |
   | TIMESTAMP | TBD2 |     0     |   Unsigned timestamp of arbitrary  |
   |           |      |           |   length, given by section, assumes that
   calculating the TLV length  |
   |           |      |           |  field. signature can be decomposed into:

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

   The MANET routing protocol |
   |           |      |           |   has to define how hash function and the cryptographic function correspond to interpret   |
   |           |      |           | the
   entries in two IANA registries, set up by 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 specification in Table 2 must be allocated from
   Section 13.

12.1.1.  Rationale

   The rationale for separating the hash function and the
   "Message TLV Types" namespace of [RFC5444].

   +-----------+------+-----------+------------------------------------+
   |    Name   | Type |    Type   |             Description            |
   |           |      | Extension |                                    |
   +-----------+------+-----------+------------------------------------+
   | SIGNATURE | TBD3 |     0     |       Signature of a message       |
   |           |      |     1     |     Signature, decomposed into     |
   |           |      |           | cryptographic
   function over into two octets instead of having all combinations in a hash |
   |           |      |           |  value,
   single octet - possibly as specified in Appendix A |
   |           |      |           | TLV type extension - is twofold: First, if
   further hash functions or cryptographic functions are added in this document.         |
   |           |      |   2-223   |            Expert Review           |
   |           |      |  224-255  |          Experimental Use          |
   | TIMESTAMP | TBD4 |     0     |   Unsigned timestamp the
   future, the number space might not remain continuous.  More
   importantly, the number space of arbitrary  |
   |           |      |           |   length, given by 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 TLV length  |
   |           |      |           |               field.               |
   |           |      |   1-223   |            Expert Review           |
   |           |      |  224-255  |          Experimental Use          |
   +-----------+------+-----------+------------------------------------+

                        Table 2: Message TLV types

12.1.4.  Address Block TLV Type Registrations foreseeable future.

   The Address Block TLVs as specified rationale for not including a field that lists parameters of the
   cryptographic signature in Table 3 must be allocated from the "Address Block TLV Types" namespace of [RFC5444].

   +-----------+------+-----------+------------------------------------+
   |    Name   | Type |    Type   |             Description            |
   |           |      | Extension |                                    |
   +-----------+------+-----------+------------------------------------+
   | SIGNATURE | TBD5 |     0     |   Signature of an object (e.g. an  |
   |           |      |           |              address)              |
   |           |      |     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 | 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 is, that before being able to
   validate a cryptographic signature, routers 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 exchange or
   acquire keys (e.g. public keys).  Any additional parameters can be
   provided together with the meanings defined keys in [BCP26]:
   "Private Use", "Expert Review", that bootstrap process.  It is
   therefore not necessary, and "Standards Action".

12.2.1.  Expert Review: Evaluation Guidelines

   For the registries for the following tables where would even entail an Expert Review extra overhead, to
   transmit the parameters within every message.  One implicitly
   available parameter is
   required, the designated expert SHOULD take length of the same general
   recommendations into consideration as are specified by [RFC5444].

12.2.2.  Hash Function

   IANA signature, which is requested to create a new registry <length>
   - 3, and which depends on the choice of the cryptographic function.

12.2.  Considerations for Calculating the hash functions
   that can Signature

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

12.2.1.  Packet SIGNATURE TLV

   When determining the <signature-value> for a signature, as specified in Packet, the
   Appendix A of this document.  The initial assignments signature is
   calculated over the three fields <hash-function>, <cryptographic-
   function> and allocation
   policies are specified <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
   message headers, in Table 4.

   +-------------+-----------+-----------------------------------------+
   |     Hash    | Algorithm |               Description               |
   |   function  |           |                                         |
   |    value    |           |                                         |
   +-------------+-----------+-----------------------------------------+
   |      0      |    none   | The "identity function": accordance with Section 8.1.

12.2.2.  Message SIGNATURE TLV

   When determining the hash value |
   |             |           |    of an object <signature-value> for a message, the signature
   is calculated over the object itself    |
   |    1-223    |           |              Expert Review              |
   |   224-255   |           |             Experimental Use            |
   +-------------+-----------+-----------------------------------------+
                      Table 4: Hash-Function registry three fields <hash-function>, <cryptographic-
   function>, and <key-index> (in that order), concatenated with the
   entire message.  The considerations in Section 9.1 MUST be applied.

12.2.3.  Cryptographic Algorithm

   IANA is requested to create a new registry  Address Block SIGNATURE TLV

   When determining the <signature-value> for an address, the cryptographic
   function, as specified in signature
   is calculated over the Appendix A of this document.  Initial
   assignments three fields <hash-function>, <cryptographic-
   function>, and allocation policies are <key-index> (in that order), concatenated with the
   address, concatenated with any other values, for example, any other
   TLV value that is associated with that address.  A MANET routing
   protocol or MANET 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.  The considerations in Section 10.2 MUST be applied.

12.3.  Example of a Signed Message

   The sample message depicted in Figure 1 is derived from appendix D of
   [RFC5444].  The message contains a SIGNATURE Message TLV, with the
   value representing a 16 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 Table 5.

   +----------------+-----------+--------------------------------------+ Section 12.

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Cryptographic PV=0 | Algorithm  PF=8  |              Description    Packet Sequence Number     | Message Type  | function value
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | MF=15 | MAL=3 |
   +----------------+-----------+--------------------------------------+      Message Length = 40      |        0 Msg. Orig Addr|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    none       Message Originator Address (cont)       |  The "identity function": the value   Hop Limit   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Hop Count   |    Message Sequence Number    |   of an encrypted hash is the hash Msg. TLV Block|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Length = 30   |   SIGNATURE   |  MTLVF = 144  |                itself  MTLVExt = 1  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |Value Len = 19 |      1-223   Hash Func   |  Crypto Func  |             Expert Review    Key Index  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     224-255                    Signature Value                            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |           Experimental Use                    Signature Value (cont)                     |
   +----------------+-----------+--------------------------------------+

                 Table 5: Cryptographic function registry
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    Signature Value (cont)                     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                    Signature Value (cont)                     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                 Figure 1: Example message with signature

13.  Security  IANA Considerations

   This document does not specify a protocol itself.  However, it
   provides a syntactical component for cryptographic signatures specification defines:

   o  two Packet TLV types, which MUST be allocated from the 0-223 range
      of
   messages and packets the "Assigned Packet TLV Types" repository of [RFC5444] as defined
      specified in [RFC5444].  It can Table 1,

   o  two Message TLV types, which MUST be used to
   address security issues allocated from the 0-127
      range of a protocol or extension that uses the
   component "Assigned Message TLV Types" repository of [RFC5444]
      as specified in this document.  As such, it has the same
   security considerations as [RFC5444].

   In addition, a protocol that includes this component Table 2,

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

   This specification requests:

   o  creation of type extension registries for these TLV types with
      initial values as the security that in Table 1 to Table 3.

   IANA is attained by the cryptographic
   signatures of a message or a packet.

   As an example, a routing protocol that uses this component requested to reject
   "badly formed" messages if a control message does not contain a valid
   signature, should indicate assign the security assumption that if same numerical value to the
   signature is valid, Packet
   TLV, Message TLV and Address Block TLV types with the message is considered valid.  It also should
   indicate the security issues that same name.

   The following terms are counteracted by this measure
   (e.g. link or identity spoofing) as well as used with the issues that are not
   counteracted (e.g. compromised keys).

14.  Acknowledgements

   The authors would like to thank Bo Berry (Cisco), Alan Cullen (BAE),
   Justin Dean (NRL), Christopher Dearlove (BAE), Paul Lambert
   (Marvell), Jerome Milan (Ecole Polytechnique) meanings defined in [BCP26]:
   "Namespace", "Assigned Value", "Registration", "Unassigned",
   "Reserved", "Hierarchical Allocation", and Henning Rogge
   (FGAN) for their constructive comments on "Designated Expert".

   The following policies are used with the document.

15.  References

15.1.  Normative References

   [BCP26]    Narten, T. meanings defined in [BCP26]:
   "Private Use", "Expert Review", and H. Alvestrand, "Guidelines "Standards Action".

13.1.  Expert Review: Evaluation Guidelines

   For the registries for Writing TLV type extensions where an
              IANA Considerations Section in RFCs", RFC 5226, BCP 26,
              May 2008.

   [RFC2119]  Bradner, S., "Key words 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 use in RFCs all Packet,
   Message and Address TLVs SHOULD be numbered identically.

13.2.  Packet TLV Type Registrations

   IANA is requested to Indicate
              Requirement Levels", RFC 2119, BCP 14, March 1997. make allocations from the "Packet TLV Types"
   namespace of [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 for the Packet TLVs specified in
              progress draft-ietf-manet-olsrv2-12.txt, July 2011.

   [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 Table 1.

   +-----------+------+-----------+------------------------------------+
   |    Name   | Type |    Type   |             Description            |
   |           |      | Extension |                                    |
   +-----------+------+-----------+------------------------------------+
   | SIGNATURE | TBD1 |     0     |        Signature TLV, as described in Section 7.  A common way of
   calculating a signature is applying a packet       |
   |           |      |     1     |     Signature, decomposed into     |
   |           |      |           | cryptographic function on over a hash value of the content.  This decomposition is |
   |           |      |           |  value, as specified in the
   following, using a type extension of 1 Section 12 |
   |           |      |           |          in this document.         |
   |           |      |   2-223   |            Expert Review           |
   |           |      |  224-255  |          Experimental Use          |
   | TIMESTAMP | TBD2 |     0     |   Unsigned timestamp of arbitrary  |
   |           |      |           |   length, given by the Signature TLVs.

A.1.  General Signature TLV Structure length  |
   |           |      |           |  field. The following data structure allows representation of a cryptographic
   signature, including specification of MANET routing protocol |
   |           |      |           |   has to define how to interpret   |
   |           |      |           |           this timestamp           |
   |           |      |   1-223   |            Expert Review           |
   |           |      |  224-255  |          Experimental Use          |
   +-----------+------+-----------+------------------------------------+

                         Table 1: Packet TLV types

13.3.  Message TLV Type Registrations

   IANA is requested to make allocations from the appropriate hash function
   and cryptographic function used "Message TLV Types"
   namespace of [RFC5444] 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, Message TLVs specified in this section, assumes that
   calculating the signature can be Table 2.

   +-----------+------+-----------+------------------------------------+
   |    Name   | Type |    Type   |             Description            |
   |           |      | Extension |                                    |
   +-----------+------+-----------+------------------------------------+
   | SIGNATURE | TBD3 |     0     |       Signature of a message       |
   |           |      |     1     |     Signature, 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 into     |
   |           |      |           | cryptographic function into two octets instead of having all combinations in over a
   single octet - possibly as TLV type extension - is twofold: First, if
   further hash functions or cryptographic functions are added |
   |           |      |           |  value, as specified in Section 12 |
   |           |      |           |          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 document.         |
   |           |      |   2-223   |            Expert Review           |
   |           |      |  224-255  |          Experimental Use          |
   | TIMESTAMP | TBD4 |     0     |   Unsigned timestamp of the
   cryptographic signature in arbitrary  |
   |           |      |           |   length, given by 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,  |
   |           |      |           |               field.               |
   |           |      |   1-223   |            Expert Review           |
   |           |      |  224-255  |          Experimental Use          |
   +-----------+------+-----------+------------------------------------+

                        Table 2: Message and TLV types

13.4.  Address
   SIGNATURE TLVs, respectively.

A.2.1.  Packet SIGNATURE Block TLV

   When determining Type Registrations

   IANA is requested to make allocations from the <signature-value> "Address Block TLV
   Types" namespace of [RFC5444] 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
   message headers.

A.2.2.  Message SIGNATURE TLV

   When determining the <signature-value> for a message, the signature
   is calculated over the three fields <hash-function>, <cryptographic-
   function>, and <key-index> (in that order), concatenated with the
   entire message.

A.2.3.  Address Block SIGNATURE TLV

   When determining the <signature-value> for an 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 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.

A.3.  Example of a Signed Message

   The sample message depicted specified in Figure 1 is derived from the appendix
   of [RFC5444].  A
   Table 3.

   +-----------+------+-----------+------------------------------------+
   |    Name   | Type |    Type   |             Description            |
   |           |      | Extension |                                    |
   +-----------+------+-----------+------------------------------------+
   | SIGNATURE Message TLV has been added, with the value
   representing a 16 octet long signature of the whole message.  The
   type extension of the Message TLV is 1, for the specific
   decomposition | TBD5 |     0     |   Signature of a signature an object (e.g. an  |
   |           |      |           |              address)              |
   |           |      |     1     |     Signature, decomposed 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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Section 12 | PV=0
   |  PF=8           |    Packet Sequence Number      | Message Type           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+          in this document.         | MF=15
   | MAL=3           |      Message Length = 40      | Msg. Orig Addr|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   2-223   |       Message Originator Address (cont)            Expert Review           |   Hop Limit
   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+           |   Hop Count      |    Message Sequence Number  224-255  | Msg.          Experimental Use          |
   | TIMESTAMP | TBD6 |     0     |   Unsigned timestamp of arbitrary  |
   |           |      |           |   length, given by the TLV Block|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ length  | Length = 30
   |   SIGNATURE           |  MTLVF = 144      |  MTLVExt = 1           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |Value Len = 19               field.               |
   |           |      |   1-223   |            Expert Review           |
   |           |      |  224-255  |          Experimental Use          |
   +-----------+------+-----------+------------------------------------+

                     Table 3: Address Block TLV types

13.5.  Hash Function

   IANA is requested to create a new registry for hash functions that
   can be used when creating a signature, as specified in Section 12 of
   this document.  The initial assignments and allocation policies are
   specified in Table 4.

   +-------------+-----------+-----------------------------------------+
   |     Hash Func    |  Crypto Func Algorithm |    Key Index               Description               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Signature Value   function  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+           |                    Signature Value (cont)                                         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Signature Value (cont)    value    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+           |                    Signature Value (cont)                                         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                 Figure 1: Example message with signature

Authors' Addresses

   Ulrich Herberg
   LIX, Ecole Polytechnique
   91128 Palaiseau Cedex,
   France
   +-------------+-----------+-----------------------------------------+
   |      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

13.6.  Cryptographic Algorithm

   IANA is requested to create a new registry for the cryptographic
   function, as specified in Section 12 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

14.  Security Considerations

   This document does not specify a protocol.  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
   MANET routing protocol or MANET routing protocol extension.  As such,
   it has the same security considerations as [RFC5444].

   In addition, a MANET routing protocol or MANET routing protocol
   extension that uses this specification 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 MANET 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).

15.  Acknowledgements

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

16.  References

16.1.  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.

16.2.  Informative References

   [OLSRv2]   Clausen, T., Dearlove, C., and P. Jacquet, "The Optimized
              Link State Routing Protocol version 2", work in
              progress draft-ietf-manet-olsrv2-12.txt, July 2011.

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

Authors' Addresses

   Ulrich Herberg
   Fujitsu Laboratories of America
   1240 E. Arques Ave. M/S 345
   Sunnyvale, CA, 94085
   USA

   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/