draft-ietf-tls-oob-pubkey-07.txt

TLS                                                      P. Wouters, Ed.
Internet-Draft                                                   Red Hat
Intended status: Standards Track                      H. Tschofenig, Ed.
Expires: August 19, 2013                          Nokia Siemens Networks
                                                              J. Gilmore

                                                               S. Weiler
                                                            SPARTA, Inc.
                                                              T. Kivinen
                                                               AuthenTec
                                                       February 15, 2013


  Out-of-Band Public Key Validation for Transport Layer Security (TLS)
                    draft-ietf-tls-oob-pubkey-07.txt

Abstract

   This document specifies a new certificate type for exchanging raw
   public keys in Transport Layer Security (TLS) and Datagram Transport
   Layer Security (DTLS) for use with out-of-band public key validation.
   Currently, TLS authentication can only occur via X.509-based Public
   Key Infrastructure (PKI) or OpenPGP certificates.  By specifying a
   minimum resource for raw public key exchange, implementations can use
   alternative public key validation methods.

   One such alternative public key valiation method is offered by the
   DNS-Based Authentication of Named Entities (DANE) together with DNS
   Security.  Another alternative is to utilize pre-configured keys, as
   is the case with sensors and other embedded devices.  The usage of
   raw public keys, instead of X.509-based certificates, leads to a
   smaller code footprint.

   This document introduces the support for raw public keys in TLS.

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



Wouters, et al.          Expires August 19, 2013                [Page 1]

Internet-Draft        TLS OOB Public Key Validation        February 2013


   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on August 19, 2013.

Copyright Notice

   Copyright (c) 2013 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.

































Wouters, et al.          Expires August 19, 2013                [Page 2]

Internet-Draft        TLS OOB Public Key Validation        February 2013


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  New TLS Extension  . . . . . . . . . . . . . . . . . . . . . .  5
   4.  TLS Handshake Extension  . . . . . . . . . . . . . . . . . . .  8
     4.1.  Client Hello . . . . . . . . . . . . . . . . . . . . . . .  8
     4.2.  Server Hello . . . . . . . . . . . . . . . . . . . . . . .  9
     4.3.  Certificate Request  . . . . . . . . . . . . . . . . . . .  9
     4.4.  Other Handshake Messages . . . . . . . . . . . . . . . . .  9
     4.5.  Client authentication  . . . . . . . . . . . . . . . . . .  9
   5.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 13
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 14
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 14
   Appendix A.  Example Encoding  . . . . . . . . . . . . . . . . . . 15
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16































Wouters, et al.          Expires August 19, 2013                [Page 3]

Internet-Draft        TLS OOB Public Key Validation        February 2013


1.  Introduction

   Traditionally, TLS server public keys are obtained in PKIX containers
   in-band using the TLS handshake and validated using trust anchors
   based on a [PKIX] certification authority (CA).  This method can add
   a complicated trust relationship that is difficult to validate.
   Examples of such complexity can be seen in [Defeating-SSL].

   Alternative methods are available that allow a TLS client to obtain
   the TLS server public key:

   o  The TLS server public key is obtained from a DNSSEC secured
      resource records using DANE [RFC6698].

   o  The TLS server public key is obtained from a [PKIX] certificate
      chain from an Lightweight Directory Access Protocol (LDAP) [LDAP]
      server.

   o  The TLS client and server public key is provisioned into the
      operating system firmware image, and updated via software updates.

   Some smart objects use the UDP-based Constrained Application Protocol
   (CoAP) [I-D.ietf-core-coap] to interact with a Web server to upload
   sensor data at a regular intervals, such as temperature readings.
   CoAP [I-D.ietf-core-coap] can utilize DTLS for securing the client-
   to-server communication.  As part of the manufacturing process, the
   embeded device may be configured with the address and the public key
   of a dedicated CoAP server, as well as a public key for the client
   itself.  The usage of X.509-based PKIX certificates [PKIX] may not
   suit all smart object deployments and would therefore be an
   unneccesarry burden.

   The Transport Layer Security (TLS) Protocol Version 1.2 [RFC5246]
   provides a framework for extensions to TLS as well as guidelines for
   designing such extensions.  This document registers a new value to
   the IANA certificate types registry for the support of raw public
   keys.


2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].







Wouters, et al.          Expires August 19, 2013                [Page 4]

Internet-Draft        TLS OOB Public Key Validation        February 2013


3.  New TLS Extension

   This section describes the changes to the TLS handshake message
   contents when raw public key certificates are to be used.  Figure 4
   illustrates the exchange of messages as described in the sub-sections
   below.  The client and the server exchange make use of two new TLS
   extensions, namely 'client_certificate_type' and
   'server_certificate_type', and an already available IANA TLS
   Certificate Type registry [TLS-Certificate-Types-Registry] to
   indicate their ability and desire to exchange raw public keys.  These
   raw public keys, in the form of a SubjectPublicKeyInfo structure, are
   then carried inside the Certificate payload.  The Certificate and the
   SubjectPublicKeyInfo structure is shown in Figure 1.



   opaque ASN.1Cert<1..2^24-1>;

   struct {
           select(certificate_type){

                   // certificate type defined in this document.
           case RawPublicKey:
             opaque ASN.1_subjectPublicKeyInfo<1..2^24-1>;

                   // X.509 certificate defined in RFC 5246
           case X.509:
                     ASN.1Cert certificate_list<0..2^24-1>;

                   // Additional certificate type based on TLS
           // Certificate Type Registry
           };
   } Certificate;


                   Figure 1: TLS Certificate Structure.

   The SubjectPublicKeyInfo structure is defined in Section 4.1 of RFC
   5280 [PKIX] and does not only contain the raw keys, such as the
   public exponent and the modulus of an RSA public key, but also an
   algorithm identifier.  The structure, as shown in Figure 2, is
   encoded in an ASN.1 format and therefore contains length information
   as well.  An example is provided in Appendix A.








Wouters, et al.          Expires August 19, 2013                [Page 5]

Internet-Draft        TLS OOB Public Key Validation        February 2013


      SubjectPublicKeyInfo  ::=  SEQUENCE  {
           algorithm            AlgorithmIdentifier,
           subjectPublicKey     BIT STRING  }


              Figure 2: SubjectPublicKeyInfo ASN.1 Structure.

   The algorithm identifiers are Object Identifiers (OIDs).  RFC 3279
   [RFC3279], for example, defines the following OIDs shown in Figure 3.



Key Type               | Document                   | OID
-----------------------+----------------------------+-------------------
RSA                    | Section 2.3.1 of RFC 3279  | 1.2.840.113549.1.1
.......................|............................|...................
Digital Signature      |                            |
Algorithm (DSS)        | Section 2.3.2 of RFC 3279  | 1.2.840.10040.4.1
.......................|............................|...................
Elliptic Curve         |                            |
Digital Signature      |                            |
Algorithm (ECDSA)      | Section 2.3.5 of RFC 3279  | 1.2.840.10045.2.1
-----------------------+----------------------------+-------------------


                 Figure 3: Example Algorithm Identifiers.

   The message exchange in Figure 4 shows the 'client_certificate_type'
   and 'server_certificate_type' extensions added to the client and
   server hello messages.





















Wouters, et al.          Expires August 19, 2013                [Page 6]

Internet-Draft        TLS OOB Public Key Validation        February 2013


    client_hello,
    client_certificate_type
    server_certificate_type   ->

                              <-  server_hello,
                                  client_certificate_type,
                                  server_certificate_type,
                                  certificate,
                                  server_key_exchange,
                                  certificate_request,
                                  server_hello_done
    certificate,
    client_key_exchange,
    certificate_verify,
    change_cipher_spec,
    finished                  ->

                              <- change_cipher_spec,
                                 finished

   Application Data        <------->     Application Data


               Figure 4: Basic Raw Public Key TLS Exchange.

   The semantic of the two extensions is defined as follows:

      The 'client_certificate_type' and 'server_certificate_type' sent
      in the client hello, may carry a list of supported certificate
      types, sorted by client preference.  It is a list in the case
      where the client supports multiple certificate types.  These
      extension MUST be omitted if the client only supports X.509
      certificates.  The 'client_certificate_type' sent in the client
      hello indicates the certificate types the client is able to
      provide to the server, when requested using a certificate_request
      message.  The 'server_certificate_type' in the client hello
      indicates the type of certificates the client is able to process
      when provided by the server in a subsequent certificate payload.

      The 'client_certificate_type' returned in the server hello
      indicates the certificate type found in the attached certificate
      payload.  Only a single value is permitted.  The
      'server_certificate_type' in the server hello indicates the type
      of certificates the client is requested to provide in a subsequent
      certificate payload.  The value conveyed in the
      'server_certificate_type' MUST be selected from one of the values
      provided in the 'server_certificate_type' sent in the client
      hello.  If the server does not send a certificate_request payload



Wouters, et al.          Expires August 19, 2013                [Page 7]

Internet-Draft        TLS OOB Public Key Validation        February 2013


      or none of the certificates supported by the client (as indicated
      in the 'server_certificate_type' in the client hello) match the
      server-supported certificate types the 'server_certificate_type'
      payload sent in the server hello is omitted.

   The "extension_data" field of this extension contains the
   ClientCertTypeExtension or the ServerCertTypeExtension structure, as
   shown in Figure 5.  The CertificateType structure is an enum with
   with values from TLS Certificate Type Registry.



   struct {
           select(ClientOrServerExtension)
               case client:
                 CertificateType client_certificate_types<1..2^8-1>;
               case server:
                 CertificateType client_certificate_type;
           }
   } ClientCertTypeExtension;

   struct {
           select(ClientOrServerExtension)
               case client:
                 CertificateType server_certificate_types<1..2^8-1>;
               case server:
                 CertificateType server_certificate_type;
           }
   } ServerCertTypeExtension;


                  Figure 5: CertTypeExtension Structure.

   No new cipher suites are required to use raw public keys.  All
   existing cipher suites that support a key exchange method compatible
   with the defined extension can be used.


4.  TLS Handshake Extension

4.1.  Client Hello

   In order to indicate the support of out-of-band raw public keys,
   clients MUST include the 'client_certificate_type' and
   'server_certificate_type' extensions extended client hello message.
   The hello extension mechanism is described in TLS 1.2 [RFC5246].





Wouters, et al.          Expires August 19, 2013                [Page 8]

Internet-Draft        TLS OOB Public Key Validation        February 2013


4.2.  Server Hello

   If the server receives a client hello that contains the
   'client_certificate_type' and 'server_certificate_type' extensions
   and chooses a cipher suite then three outcomes are possible:

   1.  The server does not support the extension defined in this
       document.  In this case the server returns the server hello
       without the extensions defined in this document.

   2.  The server supports the extension defined in this document and
       has at least one certificate type in common with the client.  In
       this case it returns the 'server_certificate_type' and indicates
       the selected certificate type value.

   3.  The server supports the extension defined in this document but
       does not have a certificate type in common with the client.  In
       this case the server terminate the session with a fatal alert of
       type "unsupported_certificate".

   If the TLS server also requests a certificate from the client (via
   the certificate_request) it MUST include the
   'client_certificate_type' extension with a value chosen from the list
   of client-supported certificates types (as provided in the
   'client_certificate_type' of the client hello).

   If the client indicated the support of raw public keys in the
   'client_certificate_type' extension in the client hello and the
   server is able to provide such raw public key then the TLS server
   MUST place the SubjectPublicKeyInfo structure into the Certificate
   payload.  The public key algorithm MUST match the selected key
   exchange algorithm.

4.3.  Certificate Request

   The semantics of this message remain the same as in the TLS
   specification.

4.4.  Other Handshake Messages

   All the other handshake messages are identical to the TLS
   specification.

4.5.  Client authentication

   Client authentication by the TLS server is supported only through
   authentication of the received client SubjectPublicKeyInfo via an
   out-of-band method.



Wouters, et al.          Expires August 19, 2013                [Page 9]

Internet-Draft        TLS OOB Public Key Validation        February 2013


5.  Examples

   Figure 6, Figure 7, and Figure 8 illustrate example exchanges.

   The first example shows an exchange where the TLS client indicates
   its ability to receive and validate raw public keys from the server.
   In our example the client is quite restricted since it is unable to
   process other certificate types sent by the server.  It also does not
   have credentials (at the TLS layer) it could send.  The
   'client_certificate_type' extension indicates this in [1].  When the
   TLS server receives the client hello it processes the
   'client_certificate_type' extension.  Since it also has a raw public
   key it indicates in [2] that it had choosen to place the
   SubjectPublicKeyInfo structure into the Certificate payload [3].  The
   client uses this raw public key in the TLS handshake and an out-of-
   band technique, such as DANE, to verify its validity.



client_hello,
server_certificate_type=(RawPublicKey) -> // [1]

                         <-  server_hello,
                             server_certificate_type=(RawPublicKey), // [2]
                             certificate, // [3]
                             server_key_exchange,
                             server_hello_done

client_key_exchange,
change_cipher_spec,
finished                  ->

                         <- change_cipher_spec,
                            finished

Application Data        <------->     Application Data


     Figure 6: Example with Raw Public Key provided by the TLS Server

   In our second example the TLS client as well as the TLS server use
   raw public keys.  This is a use case envisioned for smart object
   networking.  The TLS client in this case is an embedded device that
   is configured with a raw public key for use with TLS and is also able
   to process raw public keys sent by the server.  Therefore, it
   indicates these capabilities in [1].  As in the previously shown
   example the server fulfills the client's request, indicates this via
   the "RawPublicKey" value in the server_certificate_type payload, and



Wouters, et al.          Expires August 19, 2013               [Page 10]

Internet-Draft        TLS OOB Public Key Validation        February 2013


   provides a raw public key into the Certificate payload back to the
   client (see [3]).  The TLS server, however, demands client
   authentication and therefore a certificate_request is added [4].  The
   certificate_type payload in [2] indicates that the TLS server accepts
   raw public keys.  The TLS client, who has a raw public key pre-
   provisioned, returns it in the Certificate payload [5] to the server.



client_hello,
client_certificate_type=(RawPublicKey) // [1]
server_certificate_type=(RawPublicKey) // [1]
                         ->
                         <-  server_hello,
                             server_certificate_type=(RawPublicKey)//[2]
                             certificate, // [3]
                             client_certificate_type=(RawPublicKey)//[4]
                             certificate_request, // [4]
                             server_key_exchange,
                             server_hello_done

certificate, // [5]
client_key_exchange,
change_cipher_spec,
finished                  ->

                         <- change_cipher_spec,
                            finished

Application Data        <------->     Application Data


   Figure 7: Example with Raw Public Key provided by the TLS Server and
                                the Client

   In our last example we illustrate a combination of raw public key and
   X.509 usage.  The client uses a raw public key for client
   authentication but the server provides an X.509 certificate.  This
   exchange starts with the client indicating its ability to process
   X.509 certificates provided by the server, and the ability to send
   raw public keys (see [1]).  The server provides the X.509 certificate
   in [3] with the indication present in [2].  For client authentication
   the server indicates in [4] that it selected the raw public key
   format and requests a certificate from the client in [5].  The TLS
   client provides a raw public key in [6] after receiving and
   processing the TLS server hello message.





Wouters, et al.          Expires August 19, 2013               [Page 11]

Internet-Draft        TLS OOB Public Key Validation        February 2013


client_hello,
server_certificate_type=(X.509)
client_certificate_type=(RawPublicKey) // [1]
                         ->
                         <-  server_hello,
                             server_certificate_type=(X.509)//[2]
                             certificate, // [3]
                             client_certificate_type=(RawPublicKey)//[4]
                             certificate_request, // [5]
                             server_key_exchange,
                             server_hello_done
certificate, // [6]
client_key_exchange,
change_cipher_spec,
finished                  ->

                          <- change_cipher_spec,
                             finished

Application Data        <------->     Application Data


                   Figure 8: Hybrid Certificate Example


6.  Security Considerations

   The transmission of raw public keys, as described in this document,
   provides benefits by lowering the over-the-air transmission overhead
   since raw public keys are quite naturally smaller than an entire
   certificate.  There are also advantages from a codesize point of view
   for parsing and processing these keys.  The crytographic procedures
   for assocating the public key with the possession of a private key
   also follows standard procedures.

   The main security challenge is, however, how to associate the public
   key with a specific entity.  This information will be needed to make
   authorization decisions.  Without a secure binding, man-in-the-middle
   attacks may be the consequence.  This document assumes that such
   binding can be made out-of-band and we list a few examples in
   Section 1.  DANE [RFC6698] offers one such approach.  If public keys
   are obtained using DANE, these public keys are authenticated via
   DNSSEC.  Pre-configured keys is another out of band method for
   authenticating raw public keys.  While pre-configured keys are not
   suitable for a generic Web-based e-commerce environment such keys are
   a reasonable approach for many smart object deployments where there
   is a close relationship between the software running on the device
   and the server-side communication endpoint.  Regardless of the chosen



Wouters, et al.          Expires August 19, 2013               [Page 12]

Internet-Draft        TLS OOB Public Key Validation        February 2013


   mechanism for out-of-band public key validation an assessment of the
   most suitable approach has to be made prior to the start of a
   deployment to ensure the security of the system.


7.  IANA Considerations

   IANA is asked to register a new value in the "TLS Certificate Types"
   registry of Transport Layer Security (TLS) Extensions
   [TLS-Certificate-Types-Registry], as follows:


   Value: 2
   Description: Raw Public Key
   Reference: [[THIS RFC]]


   This document asks IANA to allocate two new TLS extensions,
   "client_certificate_type" and "server_certificate_type", from the TLS
   ExtensionType registry defined in [RFC5246].  These extensions are
   used in both the client hello message and the server hello message.
   The new extension type is used for certificate type negotiation.  The
   values carried in these extensions are taken from the TLS Certificate
   Types registry [TLS-Certificate-Types-Registry].


8.  Acknowledgements

   The feedback from the TLS working group meeting at IETF#81 has
   substantially shaped the document and we would like to thank the
   meeting participants for their input.  The support for hashes of
   public keys has been moved to [I-D.ietf-tls-cached-info] after the
   discussions at the IETF#82 meeting.

   We would like to thank the following persons for their review
   comments: Martin Rex, Bill Frantz, Zach Shelby, Carsten Bormann,
   Cullen Jennings, Rene Struik, Alper Yegin, Jim Schaad, Barry Leiba,
   Paul Hoffman, Robert Cragie, Nikos Mavrogiannopoulos, Phil Hunt, John
   Bradley, Klaus Hartke, Stefan Jucker, Kovatsch Matthias, Daniel Kahn
   Gillmor, and James Manger.  Nikos Mavrogiannopoulos contributed the
   design for re-using the certificate type registry.  Barry Leiba
   contributed guidance for the IANA consideration text.  Stefan Jucker,
   Kovatsch Matthias, and Klaus Hartke provided implementation feedback
   regarding the SubjectPublicKeyInfo structure.

   Finally, we would like to thank our TLS working group chairs, Eric
   Rescorla and Joe Salowey, for their guidance and support.




Wouters, et al.          Expires August 19, 2013               [Page 13]

Internet-Draft        TLS OOB Public Key Validation        February 2013


9.  References

9.1.  Normative References

   [PKIX]     Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, May 2008.

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

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246, August 2008.

   [TLS-Certificate-Types-Registry]
              "TLS Certificate Types Registry", February 2013, <http://
              www.iana.org/assignments/
              tls-extensiontype-values#tls-extensiontype-values-2>.

9.2.  Informative References

   [ASN.1-Dump]
              Gutmann, P., "ASN.1 Object Dump Program", February 2013,
              <http://www.cs.auckland.ac.nz/~pgut001/>.

   [Defeating-SSL]
              Marlinspike, M., "New Tricks for Defeating SSL in
              Practice", February 2009, <http://www.blackhat.com/
              presentations/bh-dc-09/Marlinspike/
              BlackHat-DC-09-Marlinspike-Defeating-SSL.pdf>.

   [I-D.ietf-core-coap]
              Shelby, Z., Hartke, K., Bormann, C., and B. Frank,
              "Constrained Application Protocol (CoAP)",
              draft-ietf-core-coap-13 (work in progress), December 2012.

   [I-D.ietf-tls-cached-info]
              Santesson, S. and H. Tschofenig, "Transport Layer Security
              (TLS) Cached Information Extension",
              draft-ietf-tls-cached-info-13 (work in progress),
              September 2012.

   [LDAP]     Sermersheim, J., "Lightweight Directory Access Protocol
              (LDAP): The Protocol", RFC 4511, June 2006.

   [RFC3279]  Bassham, L., Polk, W., and R. Housley, "Algorithms and
              Identifiers for the Internet X.509 Public Key



Wouters, et al.          Expires August 19, 2013               [Page 14]

Internet-Draft        TLS OOB Public Key Validation        February 2013


              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 3279, April 2002.

   [RFC6698]  Hoffman, P. and J. Schlyter, "The DNS-Based Authentication
              of Named Entities (DANE) Transport Layer Security (TLS)
              Protocol: TLSA", RFC 6698, August 2012.


Appendix A.  Example Encoding

   For example, the following hex sequence describes a
   SubjectPublicKeyInfo structure inside the certificate payload:


          0     1     2     3     4     5     6     7     8     9
   ---+------+-----+-----+-----+-----+-----+-----+-----+-----+-----
   1  | 0x30, 0x81, 0x9f, 0x30, 0x0d, 0x06, 0x09, 0x2a, 0x86, 0x48,
   2  | 0x86, 0xf7, 0x0d, 0x01, 0x01, 0x01, 0x05, 0x00, 0x03, 0x81,
   3  | 0x8d, 0x00, 0x30, 0x81, 0x89, 0x02, 0x81, 0x81, 0x00, 0xcd,
   4  | 0xfd, 0x89, 0x48, 0xbe, 0x36, 0xb9, 0x95, 0x76, 0xd4, 0x13,
   5  | 0x30, 0x0e, 0xbf, 0xb2, 0xed, 0x67, 0x0a, 0xc0, 0x16, 0x3f,
   6  | 0x51, 0x09, 0x9d, 0x29, 0x2f, 0xb2, 0x6d, 0x3f, 0x3e, 0x6c,
   7  | 0x2f, 0x90, 0x80, 0xa1, 0x71, 0xdf, 0xbe, 0x38, 0xc5, 0xcb,
   8  | 0xa9, 0x9a, 0x40, 0x14, 0x90, 0x0a, 0xf9, 0xb7, 0x07, 0x0b,
   9  | 0xe1, 0xda, 0xe7, 0x09, 0xbf, 0x0d, 0x57, 0x41, 0x86, 0x60,
   10 | 0xa1, 0xc1, 0x27, 0x91, 0x5b, 0x0a, 0x98, 0x46, 0x1b, 0xf6,
   11 | 0xa2, 0x84, 0xf8, 0x65, 0xc7, 0xce, 0x2d, 0x96, 0x17, 0xaa,
   12 | 0x91, 0xf8, 0x61, 0x04, 0x50, 0x70, 0xeb, 0xb4, 0x43, 0xb7,
   13 | 0xdc, 0x9a, 0xcc, 0x31, 0x01, 0x14, 0xd4, 0xcd, 0xcc, 0xc2,
   14 | 0x37, 0x6d, 0x69, 0x82, 0xd6, 0xc6, 0xc4, 0xbe, 0xf2, 0x34,
   15 | 0xa5, 0xc9, 0xa6, 0x19, 0x53, 0x32, 0x7a, 0x86, 0x0e, 0x91,
   16 | 0x82, 0x0f, 0xa1, 0x42, 0x54, 0xaa, 0x01, 0x02, 0x03, 0x01,
   17 | 0x00, 0x01


      Figure 9: Example SubjectPublicKeyInfo Structure Byte Sequence.

   The decoded byte-sequence shown in Figure 9 (for example using
   Peter's ASN.1 decoder [ASN.1-Dump]) illustrates the structure, as
   shown in Figure 10.











Wouters, et al.          Expires August 19, 2013               [Page 15]

Internet-Draft        TLS OOB Public Key Validation        February 2013


   Offset  Length   Description
   -------------------------------------------------------------------
      0     3+159:   SEQUENCE {
      3      2+13:     SEQUENCE {
      5       2+9:      OBJECT IDENTIFIER Value (1 2 840 113549 1 1 1)
                 :             PKCS #1, rsaEncryption
     16       2+0:      NULL
                 :      }
     18     3+141:    BIT STRING, encapsulates {
     22     3+137:      SEQUENCE {
     25     3+129:        INTEGER Value (1024 bit)
    157       2+3:        INTEGER Value (65537)
                 :        }
                 :      }
                 :    }


      Figure 10: Decoding of Example SubjectPublicKeyInfo Structure.


Authors' Addresses

   Paul Wouters (editor)
   Red Hat


   Email: paul@nohats.ca


   Hannes Tschofenig (editor)
   Nokia Siemens Networks
   Linnoitustie 6
   Espoo  02600
   Finland

   Phone: +358 (50) 4871445
   Email: Hannes.Tschofenig@gmx.net
   URI:   http://www.tschofenig.priv.at













Wouters, et al.          Expires August 19, 2013               [Page 16]

Internet-Draft        TLS OOB Public Key Validation        February 2013


   John Gilmore
   PO Box 170608
   San Francisco, California  94117
   USA

   Phone: +1 415 221 6524
   Email: gnu@toad.com
   URI:   https://www.toad.com/


   Samuel Weiler
   SPARTA, Inc.
   7110 Samuel Morse Drive
   Columbia, Maryland  21046
   US

   Email: weiler@tislabs.com


   Tero Kivinen
   AuthenTec
   Eerikinkatu 28
   HELSINKI  FI-00180
   FI

   Email: kivinen@iki.fi

























Wouters, et al.          Expires August 19, 2013               [Page 17]