draft-hallambaker-omnibroker-03.xml

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<rfc category="std" docName="draft-hallambaker-omnibroker-03" ipr="trust200902">

  <front>
    <title abbrev="OmniBroker Protocol">OmniBroker Protocol</title>
    <author fullname="Phillip Hallam-Baker" initials="P. M." surname="Hallam-Baker">
      <organization>Comodo Group Inc.</organization>
      <address>
        <email>philliph@comodo.com</email>
      </address>
    </author>
 
    <date day="30" month="July" year="2012" />

    <area>General</area>

    <workgroup>Internet Engineering Task Force</workgroup>

    <abstract>
      <t>
        An Omnibroker is an agent chosen and trusted by an Internet user to
        provide information such as name and certificate status information
        that are in general trusted even if they are not trustworthy.
        Rather than acting as a mere conduit for information provided by
        existing services, an Omnibroker is responsible for curating those
        sources to protect the user.
      </t>
      <t>
        The Omnibroker Protocol (OBP) provides an aggregated interface to
        trusted Internet services including DNS, OCSP and various forms
        of authentication service. Multiple transport bindings are
        supported to permit efficient access in virtually every common
        deployment scenario and ensure access in any deployment
        scenario in which access is not being purposely denied.
      </t>

    </abstract>
  </front>

  <middle>
    <section title="Definitions">
      <section title="Requirements Language">
        <t>
          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 <xref target="RFC2119">RFC 2119</xref>.
        </t>
      </section>

    </section>
    <section title="Purpose">
      <t>
        An Omnibroker is an agent chosen and trusted by an Internet user to
        provide information such as name and certificate status information
        that are in general trusted even if they are not trustworthy.
        Rather than acting as a mere conduit for information provided by
        existing services, an Omnibroker is responsible for curating those
        sources and providing autheticated, curated results to the endpoint
        client.
      </t>
      <t>
        Unlike the traditional trusted information services that are expected
        to deliver the same response to a query regardless of who asks the
        question, OBP permits an Omnibroker to return a response that is
        tailored to the specific party asking the question. This permits the
        use of an authentication approach that has negligible impact
        on performance and permits an
        Omnibroker to answer questions that a traditional public Internet
        information service could not. In particular, an Omnibroker
        can broker peer to peer connections
      </t>
      <section title="A Curated Service">
        <t>
          In the traditional configuration, an Internet host accepts DNS service
          from the IP address specified by the local network provider, frequently
          the DNS server advertised by the local DHCP service. This approach
          creates an obvious security risk as DNS is clearly a trusted service
          and a random DNS service advertised by the local DNS is clearly not
          trustworthy.
        </t>
        <t>
          A policy of only using a chosen DNS service provides a reduction in
          risk but only a modest one since the standard DNS service does not
          provide authenticated results. Many local area networks intercept all
          DNS traffic and process it through the local DNS server regardless
          of the intended destination IP address. This practice is highly
          desirable if it would prevent a client from accessing an untrustworthy
          DNS service in place of a trustworthy local DNS service and
          extreemly undesirable in the contrary case.
        </t>
        <t>
          In addition to ensuring the authenticity of DNS resolution responses,
          such services frequently provide filtering of Internet addresses
          the network provider considers undesirable. Many workplaces block access
          to Web sites that are considered detrimental to productivity.
          Many parent subscribe to services that filter content they consider
          undesirable. While the value of such services is debatable they
          are services that those customers have chosen to deploy on their
          networks to meet their perceived security requirements. New security
          proposals that do not support such capabilities or seek to
          actually circumvent them will not be acceptable to those
          constituencies.
        </t>
        <t>
          While DNS filtering is a form of censorship, not all forms of
          DNS filering are intrinsically undesirable censorship. Spam filtering
          is also a form of censorship albeit one that is not normally
          regarded as such because it most Internet users now consider it to
          be an essential security control. Anti-Virus tools are also a form
          of censorship. DNS filtering tools that block access to sites that
          distribute malware are also a form of censorship and are rapidly
          gaining popularity for the same reason.
        </t>
        <t>
          While all forms of censorship raise civil liberties concerns,
          censorship should not automatically raise civil liberties objections.
          It is not the fact that filtering is taking place but
          the party that is in control of the filtering that should
          raise civil liberties concerns. In an Internet of
          2 billion users, all users are obliged to perform some filtering.
          OBP is designed to make the party that is in control of the
          filtering process apparent and provide the end user with the
          ability to select the Omnibroker of their choice.
        </t>
        <t>
          DNSSEC provides a means of determining that a DNS record is the
          authentic record published by the source but this capability alone
          does not meet the security requirements for DNS resolution services
          as they have come to be understood since the protocol was first proposed.
        </t>
        <t>
          Internet users want to be safe from all forms of attack, not just
          the DNS resolver mani-in-the-middle attack that 'end-to-end'
          deployment of DNSSEC is designed to address. An Internet user is
          far more likely to be directed to a site with a DNS name controlled
          by a criminal gang than be subject to a man-in-the-middle attack.
        </t>
        <t>
          Most users would prefer to have an Internet connection that is
          'curated' to remove at least some of the locations they consider
          to be undesirable. The fact that an organised criminal gang has put
          a host on the Internet does not mean that any other Internet user
          should be obliged to allow it to connect to any of the machines that
          they own.
        </t>
        <t>
          The same argument for curating the raw results applies to
          other forms of trusted information service. The fact that a
          Certificate Authority has issued a digital certificate and
          considers it to be valid should not mean that the end party
          is automatically considered trustworthy by anyone and for
          any purpose.
        </t>
        <t>
          The deployment of security policy capabilities presents another
          case in which direct reliance on raw data is undesirable. While
          security policies such as 'host always offers TLS' or 'mail
          server always signs outgoing mail with DKIM' can provide
          considerable security advantages, only some of the security
          policy information that is published is accurate and kept
          up to date. Curating such data sources typically proves
          essential if an unacceptable rate of false positives is
          to be avoided.
        </t>
        <t>
          Although a client is permitted to curate its own data sources
          it rarely has a sufficient amount of data to make decisions
          as accurately as a network service that can draw on a wide
          variety of additional data including tracking of communication
          patterns, historical data series and third party reputation
          services.
        </t>
        <t>
          Curation in the network offers better asgility than the client
          approach. Agility is an important consideration when an attacker
          changes their strategy rapidly and repeatedly to counter
          new defensive controls.
        </t>
        <t>
          While curating trusted data sources is an established and
          proven practice, current practice has been to curate each
          source individually. This approach avoids the need to write
          a new protocol but limits the information a curator can
          leverage to detect potential danger. Leveraging multiple
          data sources simultaneously allows better accuracy than
          applying each individually.
        </t>
      </section>

      <section title="Connection Broker">
        <t>
          The OBP service connection broker answers the query 'what connection
          parameters should be used to establish the best connection
          to interract with party X according to protocol Y. Where 'best'
          is determined by the Omnibroker which MAY take into account
          parameters specified by the relying party.
        </t>
        <section title="Service Connection Broker">
          <t>
            The OBP service connection broker supports and extends the traditional
            DNS resolution service that resolves a DNS name (e.g. www.example.com) to
            return an IP address (e.g. 10.1.2.3).
          </t>
          <t>
            When using an Omnibroker as a service connection broker, a client
            specifies both the DNS name (e.g. www.example.com) and the
            Internet protocol to be used (e.g. _http._tcp). The returned
            connection parameters MAY include:
          </t>
          <t>
            <list>
              <t>
                The IP protocol version, address and port number to
                establish a connection to.
              </t>
              <t>
                If appropriate, a security transport such as TLS or IPSEC.
              </t>
              <t>
                If appropriate, a description of a service credential such
                as a TLS certificate or a constraint on the type of certificates
                that the client should consider acceptable.
              </t>
              <t>
                If appropriate, application protocol details such as
                version and protocol options.
              </t>
            </list>
          </t>
          <t>
            If an attempt to connect with the parameters specified fails, a
            client MAY report the failure and request a new set of parameters.
          </t>

        </section>
        <section title="Peer Connection Broker">
          <t>
            Each OBP request identifies both the account under which the
            request is made and the device from which it is made. An OBP broker
            is thus capable of acting as a peer connection broker service
            or providing a gateway to such a service.
          </t>
          <t>
            When using Omnibroker as a peer connection broker, a client
            specifies the account name and DNS name of the party with which
            a connection is to be established (e.g. alice@example.com)
            and the connection protocol to be used (e.g. _xmpp-client._tcp)
          </t>
          <t>
            The returned
            connection parameters are similar to those returned in response to a
            service broker query.
          </t>
        </section>
        <section title="Connection Broker API">
          <t>
            In the traditional BSD sockets API a network client performs
            a series of calls to resolve a network name to a list of IP
            addresses, selects one and establishes an IP connection to
            a port specified by the chosen application protocol.
          </t>

          <t>
            OBP anticipates a higher level abstract API that encapsulates
            this complexity, hiding it from the application code.
          </t>
          <t>
            In the case that one (or more) OBP services are configured,
            the library supporting the SHOULD obtain connection parameters
            from the OBP service. Otherwise, it SHOULD establish a connection
            using the traditional calling sequence of resolving a host
            name to obtain an IP address, etc.
          </t>
        </section>
      </section>

      <section title="Service Advertisement">
        <t>
          Service advertisement is the converse of service resolution. An
          Internet application wishing to accept inbound connections specifies
          one or more sets of connection parameters for the Omnibroker to
          register with whatever naming, discovery or other services may
          be appropriate.
        </t>
        <t>

        </t>
        <section title="Connection Advertisement API">
          <t>
            OBP anticipates the use of a high level API for connection advertisement
            that is the converse of the Connection broker API. Instead
            of establishing a connection, the API is used to advertise
            that a connection is offered either as a service or a peer.
          </t>

          <t>
            An application MAY offer multiple types of connection with
            different connection properties (e.g. IPv4/IPv6, with and
            without SSL, etc.). This MAY be supported by marking certain
            properties as being optional and/or by permitting the
            API to be called multiple times with different properties
            specified.
          </t>
        </section>
      </section>
      <section title="Credential Validation Broker">
        <t>
          A credential validation broker reports on the validity and
          trustworthiness of credentials presented to a client by Internet
          services and/or peers.
        </t>
        <t>
          The service provided by OBP is similar to that provided by
          OCSP and SCVP. Like SCVP, OBP is an agent selected by the
          relying party to validate certificates and/or construct
          trust paths on its behalf.
        </t>
      </section>
      <section title="Authentication Gateway">
        <t>
          Every OBP request is strongly authenticated by means of a shared
          secret that is unique to the account and the device. This may be
          leveraged to permit use as an authentication gateway, providing
          access to other credentials that the client has established the
          right to use.
        </t>
        <t>
          An Authentication Gateway MAY provide access to account names and
          passwords that the account holder has chosen to store in the cloud for
          access to sites that do not support a stronger,
          cryptographically based form of
          authentication such as OAuth.
        </t>
      </section>
      <section title="Credential Announcement">
        <t>
          An Authentication Gateway can only provide access to credentials
          that it has notice of. A client uses the Credential Announcement
          transaction to advise the service of a new credential.
        </t>
      </section>
      
    </section>

    <section title="Omnibroker Connection Maintenance Service">

      <section title="Authentication">
        <t>
          The principle function of the OBP Connection Maintenance Protocol
          is to establish and maintain the cryptographic parameters
          used to authenticate and encrypt
        </t>
        <t>
          The user needs to authenticate the broker service regardless
          of any authentication requirements of the broker.
        </t>
        <section title="Broker Authentication">


          <t>

            The OBP connection maintenance protocol transport MUST provide
            a trustworthy means of verifying the identity of the broker
            (e.g. an Extended Validation SSL certificate).
          </t>
          <t>
            If the device supports a display capability, authentication of the
            device and user MAY be achieved by means of an authentication
            image. Such an authentication image is generated by the broker and
            passed to the client in the OpenResponse message. The user then
            verifies that the image presented on the device display is the same
            as that presented on the account maintenance console.
          </t>

        </section>
        <section title="Device Authentication">
          <t>
            If device authentication is required, the mechanism to be used depends on
            the capabilities of the device, the requirements of the broker and
            the existing relationship between the user and the broker.
          </t>

          <t>
            If the device supports some means of data entry, authentication
            MAY be achieved by entering a passcode into the device that was
            previously delivered to the user out of band.
          </t>
          <t>
            The passcode authentication mechanism allows the device to establish
            a proof that it knows the passcode without disclosing the passcode.
            This property provides protection against Man-In-The-Middle type
            disclosure attacks.
          </t>


        </section>

        <!-- Begin section of automatically generated text
Line wrap = 66
   -->
        <section title="Illustrative example" anchor="ConnectionRequestExample">
          <t>
            Alice is an employee of Example Inc. which runs its own
            local omnibroker service 'example.com'.  
To configure her machine for use
            with this service, Alice contacts her network
            administrator who assigns her the account identifier
            'alice' and obtains a PIN number from the service  
            'PP00D0-3H8N0D-H029'
          </t>
          <t>
            Alice enters the values 'alice@example.com' and
            'PP00D0-3H8N0D-H029' into her Omnibroker-enabled  
            Web browser.
          </t>
          
          <t>
            The Web browser uses the local DNS to resolve
            'example.com'
            and establishes a HTTPS connection to the specified IP
             address.
            The client verifies that the certificate presented has
             a valid
            certificate chain to an embedded trust anchor under an  
            appropriate certificate policy (e.g. compliant with
            Extended Validation
            Criteria defined by CA-Browser Forum).
          </t>
          <t>
            Having established an authenticated and encrypted TLS  
            session to the Omnibroker service, the client sends
            an OpenRequest message to begin the process of mutual  
            authentication. This message specifies the
            cryptographic
            parameters supported by the client (Authentication,
            Encryption)
            and a nonce value (Challenge), device identification
            parameters (DeviceID, DeviceURI, DeviceName) and the
            name of the account being requested.
          </t>
          <t>
            The client does not specify the PIN code in the
            request,  
            nor is the request authenticated. Instead the client
            informs
            the server that it has a PIN code that can be supplied
             if
            necessary.  
          </t>
          <figure>
            <artwork>
<![CDATA[Post / HTTP/1.1
Host: example.com
Cache-Control: no-store
Content-Type: Application/json;charset=UTF-8
Content-Length: 470

{
  "OpenRequest": {
    "Encryption": ["HS256",
      "HS384",
      "HS512",
      "HS256T128"],
    "Authentication": ["A128CBC",
      "A256CBC",
      "A128GCM",
      "A256GCM"],
    "Account": "alice",
    "Domain": "example.com",
    "HavePasscode": true,
    "HaveDisplay": true,
    "Challenge": "8MrTu7E0ZmM1fohlpt1PxQ==",
    "DeviceID": "Serial:0002212",
    "DeviceURI": "http://comodo.com/dragon/v3.4",
    "DeviceName": "Comodo Dragon"}}]]>
            </artwork>
          </figure>

          <t>
            The service receives the request. If the request is
            consistent  
            with the access control policy for the server it
            returns a  
            reply that specifies the chosen cryptographic
            parameters  
            (Cryptographic), responds to the client issued by the  
            client to establish server proof of knowsledge of the
             PIN
            (ChallengeResponse) and issues a challenge to the
            client  
            (Challenge).
          </t>
          <t>
            The cryptographic parameters specify algorithms to be
             used  
            for encryption and authentication, a shared secret and
             a  
            ticket value. Note that while the shared secret is
            exchanged  
            in plaintext form in the HTTP binding, the connection
            protocol MUST provide encryption.
          </t>
          <figure>
            <artwork>
<![CDATA[HTTP/1.1 203 Passcode
Content-Type: application/json;charset=UTF-8
Content-Length: 500

{
  "OpenResponse": {
    "Status": 203,
    "StatusDescription": "Passcode",
    "Cryptographic": [{
        "Secret": "xlE2Bu6cMf3Y9x29tsP5WQ==",
        "Encryption": "A128CBC",
        "Authentication": "HS256",
        "Ticket":
        "hyBNCDyVadjnkSzNp4goyQ+QR9jw/TnF5jQrkl66QhQbcfxSfTj+kxjzWt
        3s6z9X2KMziSerHpLmw7DPoCg8OM1MHSt5PHHssfPvH6eaU+PxREiqMMFSI
        7k9MFh53dTWJ8Sp6Q+/dN9LnvwgZ5P83w=="}],
    "Challenge": "PrE0hkZefumcw17yuYHz+w==",
    "ChallengeResponse": "0lXrJqm6JmeWoCGmoV3Yhg=="}}]]>
            </artwork>
          </figure>

          <t>
            To complete the transaction, the client sends a
            TicketRequest message
            to the serice containing a response to the PIN
            challenge sent by the
            service (ChallengeResponse).
            The TicketRequest message is authenticated under the
            shared secret specified
            in the OpenResponse message.
          </t>

          <figure>
            <artwork>
<![CDATA[Post / HTTP/1.1
Host: example.com
Cache-Control: no-store
Content-Type: Application/json;charset=UTF-8
Content-Length: 78
Content-Integrity:
  mac=W2T7RzLP9DqmRT8wQxGnDUoCtatkAnbHm/k4ZcpsaCk=;
  ticket=hyBNCDyVadjnkSzNp4goyQ+QR9jw/TnF5jQrkl66QhQbcfxSfTj+kxjzWt
    3s6z9X2KMziSerHpLmw7DPoCg8OM1MHSt5PHHssfPvH6eaU+PxREiqMMFSI7k9M
    Fh53dTWJ8Sp6Q+/dN9LnvwgZ5P83w==

{
  "TicketRequest": {
    "ChallengeResponse": "DbZVEriNgkYjms8gCIOdDA=="}}]]>
            </artwork>
          </figure>


<t>
  If the response to the PIN challenge is correct, the service
  responds
  with a message that specifies a set of cryptographic parameters
   to be
  used to authenticate future interactions with the service
  (Cryptographic)  
  and a set of connection parameters for servers supporting the  
  Query Service (Service).
</t>
  <t>
    In this case the server returns three connections, each
    offering a
    different transport protocol option. Each connection specifies
     its
    own set of cryptographic parameters (or will when the code is
     written
    for that).
  </t>
          <figure>
            <artwork>
<![CDATA[HTTP/1.1 200 Complete
Content-Type: application/json;charset=UTF-8
Content-Length: 1907
Content-Integrity:
  mac=u4Jx2b9R8/I55h+u9PMdp6+A5++ROXeoeNR8j7CI6XM=;
  ticket=hyBNCDyVadjnkSzNp4goyQ+QR9jw/TnF5jQrkl66QhQbcfxSfTj+kxjzWt
    3s6z9X2KMziSerHpLmw7DPoCg8OM1MHSt5PHHssfPvH6eaU+PxREiqMMFSI7k9M
    Fh53dTWJ8Sp6Q+/dN9LnvwgZ5P83w==

{
  "TicketResponse": {
    "Status": 200,
    "StatusDescription": "Complete",
    "Cryptographic": [{
        "Protocol": "OBPConnection",
        "Secret": "WLZKs0IklXW4zu3B+iZ+7w==",
        "Encryption": "A128CBC",
        "Authentication": "HS256",
        "Ticket":
        "aKpbRGfe7T/6t9df72aeraC62zMNPG92ONIvZAnmztBOG2saLmQG+SkZ5r
        YLIQ6Y8e9MgD/wIgt42Z1w7C4P+I+i4QVSE9NhskTMV3hvZpE="}],
    "Service": [{
        "Name": "obp1.example.com",
        "Port": 443,
        "Address": "10.1.2.3",
        "Priority": 1,
        "Weight": 100,
        "Transport": "WebService",
        "Cryptographic": {
          "Protocol": "OBPQuery",
          "Secret": "n4An1sIfqXf+iyJCz9q+aQ==",
          "Encryption": "A128CBC",
          "Authentication": "HS256",
          "Ticket":
          "6JhkobO5VTxwwMIn2waC0+6tMoLL+vD8XmFM2oUzqFrDFVpeN9+AxdBQ
          R/KOgl5hXCJYJpKo4wQgUTV3E/QnxGcHHc2aVSiWTcna88s84sQ="}},
      {
        "Name": "dns1.example.com",
        "Port": 53,
        "Address": "10.1.2.2",
        "Priority": 1,
        "Weight": 100,
        "Transport": "DNS",
        "Cryptographic": {
          "Protocol": "OBPQuery",
          "Secret": "dgpFhrFwAF6wGxH44zHpbQ==",
          "Encryption": "A128CBC",
          "Authentication": "HS256",
          "Ticket":
          "dnx9PHts6MrrCjPGGZcV0vQdmg7NR9sQnX/07FgZmGvg1lKYopYZ7SF4
          TxTbvSXmP5vuZG+Ud3AlS1FAAX9mcUmaGTP9L+57l/QANfqlWYI="}},
      {
        "Name": "udp.example.com",
        "Port": 5000,
        "Address": "10.1.2.2",
        "Priority": 1,
        "Weight": 100,
        "Transport": "UDP",
        "Cryptographic": {
          "Protocol": "OBPQuery",
          "Secret": "4EJBvF1SepffCK3vlYvCJw==",
          "Encryption": "A128CBC",
          "Authentication": "HS256",
          "Ticket":
          "d6LVUF9kymn/1ZUSGm4T2Ht6ks3KetIAVqmkIYbX/Y9/Xga4r6sKquSy
          Mwqh7U7/ccO+6eQpNviMv4GBEzAX705TN/6hljd8oiNvvydg8YM="}}]}
          }]]>
            </artwork>
          </figure>

          <t>
            When Alice's machine is to be transfered to another
            employee, the  
            Unbind transaction is used. The only parameter
            is the
            Ticket identifying the device association (Ticket).
          </t>
          <figure>
            <artwork>
<![CDATA[Post / HTTP/1.1
Host: example.com
Cache-Control: no-store
Content-Type: Application/json;charset=UTF-8
Content-Length: 25
Content-Integrity:
  mac=GhRgO9DfsSTJ3tN1pgHKSLebN8nbIIoKsmjbaWqbZ0Q=;
  ticket=aKpbRGfe7T/6t9df72aeraC62zMNPG92ONIvZAnmztBOG2saLmQG+SkZ5r
    YLIQ6Y8e9MgD/wIgt42Z1w7C4P+I+i4QVSE9NhskTMV3hvZpE=

{
  "UnbindRequest": {}}]]>
            </artwork>
          </figure>

          <t>
            Since the unbind response represents the termination
            the
            relationship with the Omnibroker, the response merely
             reports
            the success or failure of the request.
          </t>
          <figure>
            <artwork>
<![CDATA[HTTP/1.1 0  
Content-Type: application/json;charset=UTF-8
Content-Length: 26
Content-Integrity:
  mac=Ea1qdol5hEMJ0RISG9r2oTz4KXQH8f1bZtQPVMccn04=;
  ticket=aKpbRGfe7T/6t9df72aeraC62zMNPG92ONIvZAnmztBOG2saLmQG+SkZ5r
    YLIQ6Y8e9MgD/wIgt42Z1w7C4P+I+i4QVSE9NhskTMV3hvZpE=

{
  "UnbindResponse": {}}]]>
            </artwork>
          </figure>

          <t>
            The 'Ticket' value presented in the foregoing examples
             is  
            a sequence of binary data generated by the service
            is
            opaque to the client. Services MAY generate ticket
            values  
            with a substructure that enable the service to avoid
            the need to maintain server side state.
          </t>
        <t>
          In the foregoing example, the ticket structures generated
          by the service encode the cryptographic parameter data,
          the shared secret, account identifier and an
          authentication  
          value. The initial ticket value generated additionally
          encodes
          the values of the client and service challeng values for
           use
          in calculating the necessary ChallengeResponse.
          </t>
      
        </section>

<!-- End section of automatically generated text -->

      </section>

      



<section title="OBPConnection">


<section title="Message: Message">


<!-- No parameters -->

</section>
<section title="Message: Response">


<t> <list style="hanging" hangIndent="6">
<t hangText="Status : Integer [0..1]   " />
<t>
Application layer server status code
</t>
<t hangText="StatusDescription : String [0..1]   " />
<t>
Describes the status code (ignored by processors)
</t>
</list></t>

</section>
<section title="Message: ErrorResponse">

<t>
An error response MAY be returned in response to any request.
</t>
<t>
Note that requests MAY be rejected by the code implementing
the transport binding before application processing begins
and so a server is not guaranteed to provide an error response
message.
</t>

<!-- No parameters -->

</section>
<section title="Message: Request">


<t> <list style="hanging" hangIndent="6">
<t hangText="Ticket : Binary [1..1]   " />
<t>
Opaque ticket issued by the server that identifies
the cryptographic parameters for encryption and
authentication of the message payload.
</t>
</list></t>

</section>
<section title="Structure: Cryptographic">

<t>
Parameters describing a cryptographic context.
</t>

<t> <list style="hanging" hangIndent="6">
<t hangText="Protocol : Label [0..1]   " />
<t>
OBP tickets MAY be restricted to use with either the management
protocol (Management) or the query protocol (Query). If so a 
service would typically 
specify a ticket with a long expiry time or no expiry for use with 
the management protocol and a separate ticket for use with the 
query protocol.
</t>
<t hangText="Secret : Binary [1..1]   " />
<t>
Shared secret
</t>
<t hangText="Encryption : Label [1..1]   " />
<t>
Encryption Algorithm selected
</t>
<t hangText="Authentication : Label [1..1]   " />
<t>
Authentication Algorithm selected
</t>
<t hangText="Ticket : Binary [1..1]   " />
<t>
Opaque ticket issued by the server that identifies
the cryptographic parameters for encryption and
authentication of the message payload.
</t>
<t hangText="Expires : DateTime [0..1]   " />
<t>
Date and time at which the context will expire
</t>
</list></t>

</section>
<section title="Structure: ImageLink">


<t> <list style="hanging" hangIndent="6">
<t hangText="Algorithm : Label [0..1]   " />
<t>
Image encoding algorithm (e.g. JPG, PNG)
</t>
<t hangText="Image : Binary [0..1]   " />
<t>
Image data as specified by algorithm
</t>
</list></t>

</section>
<section title="Structure: Connection">

<t>
Contains information describing a network connection.
</t>

<t> <list style="hanging" hangIndent="6">
<t hangText="Name : Name [0..1]   " />
<t>
DNS Name. Since one of the functions of an OBP service is name
resolution, a DNS name is only used to establish a connection if
connection by means of the IP address fails.
</t>
<t hangText="Port : Integer [0..1]   " />
<t>
TCP or UDP port number.
</t>
<t hangText="Address : String [0..1]   " />
<t>
IPv4 (32 bit) or IPv6 (128 bit) service address
</t>
<t hangText="Priority : Integer [0..1]   " />
<t>
Service priority. Services with lower priority numbers SHOULD
be attempted before those with higher numbers.
</t>
<t hangText="Weight : Integer [0..1]   " />
<t>
Weight to be used to select between services of equal priority.
</t>
<t hangText="Transport : Label [0..1]   " />
<t>
OBP Transport binding to be used valid values are HTTP, DNS and UDP.
</t>
<t hangText="Expires : DateTime [0..1]   " />
<t>
Date and time at which the specified connection context will expire.
</t>
</list></t>

</section>
<section title="Bind">

<t>
Binding a device is a two step protocol that begins with the
Start Query followed by a sequence of Ticket queries.
</t>

</section>
<section title="Message: BindRequest">

<t>
The following parameters MAY occur in either a
StartRequest or TicketRequest:
</t>

<t> <list style="hanging" hangIndent="6">
<t hangText="Encryption : Label [0..Many]   " />
<t>
Encryption Algorithm that the client accepts. A Client MAY
offer multiple algorithms. If no algorithms are specified then
support for the mandatory to implement algorithm is assumed.
Otherwise mandatory to implement algorithms MUST be 
specified explicitly.
</t>
<t hangText="Authentication : Label [0..Many]   " />
<t>
Authentication Algorithm that the client accepts.
If no algorithms are specified then
support for the mandatory to implement algorithm is assumed.
Otherwise mandatory to implement algorithms MUST be 
specified explicitly. 
</t>
</list></t>

</section>
<section title="Message: BindResponse">

<t>
The following parameters MAY occur in either a
StartResponse or TicketResponse:
</t>

<t> <list style="hanging" hangIndent="6">
<t hangText="Cryptographic : Cryptographic [0..Many]   " />
<t>
Cryptographic Parameters.
</t>
<t hangText="Service : Connection [0..Many]   " />
<t>
A Connection describing an OBP service point
</t>
</list></t>

</section>
<section title="Message: OpenRequest">

<t>
The OpenRequest Message is used to begin a device binding transaction.
Depending on the authentication requirements of the service the
transaction may be completed in a single query or require a 
further Ticket Query to complete.
</t>
<t>
If authentication is required, the mechanism to be used depends on
the capabilities of the device, the requirements of the broker and
the existing relationship between the user and the broker.
</t>
<t>
If the device supports some means of data entry, authentication 
MAY be achieved by entering a passcode previously delivered out
of band into the device.
</t>
<t>
The OpenRequest specifies the properties of the service
(Account, Domain) and Device (ID, URI, Name) that will remain
constant throughout the period that the device binding is active
and parameters to be used for the mutual authentication protocol.
</t>

<t> <list style="hanging" hangIndent="6">
<t hangText="Account : String [0..1]   " />
<t>
Account name of the user at the OBP service
</t>
<t hangText="Domain : Name [0..1]   " />
<t>
Domain name of the OBP broker service
</t>
<t hangText="HavePasscode : Boolean [0..1]  Default =False " />
<t>
If 'true', the user has entered a passcode value for 
use with passcode authentication.
</t>
<t hangText="HaveDisplay : Boolean [0..1]  Default =False " />
<t>
Specifies if the device is capable of displaying information
to the user or not.
</t>
<t hangText="Challenge : Binary [0..1]   " />
<t>
Client challenge value to be used in authentication challenge
</t>
<t hangText="DeviceID : URI [0..1]   " />
<t>
Device identifier unique for a particular instance of a device such as a MAC or EUI-64 address expressed as a URI
</t>
<t hangText="DeviceURI : URI [0..1]   " />
<t>
Device identifier specifying the type of device, e.g. an xPhone.
</t>
<t hangText="DeviceName : String [0..1]   " />
<t>
Descriptive name for the device that would distinguish it 
from other similar devices, e.g. 'Alice's xPhone".
</t>
</list></t>

</section>
<section title="Message: OpenResponse">

<t>
An Open request MAY be accepted immediately or be held pending
completion of an inband or out-of-band authentication process.
</t>
<t>
The OpenResponse returns a ticket and a set of cryptographic
connection parameters in either case. If the 
</t>

<t> <list style="hanging" hangIndent="6">
<t hangText="Challenge : Binary [0..1]   " />
<t>
Challenge value to be used by the client to respond
to the server authentication challenge.
</t>
<t hangText="ChallengeResponse : Binary [0..1]   " />
<t>
Server response to authentication challenge by the client
</t>
<t hangText="VerificationImage : ImageLink [0..Many]   " />
<t>
Link to an image to be used in an image verification mechanism.
</t>
</list></t>

</section>
<section title="Message: TicketRequest">

<t>
The TicketRequest message is used to (1) complete a binding request
begun with an OpenRequest and (2) to refresh ticket or connection 
parameters as necessary.
</t>

<t> <list style="hanging" hangIndent="6">
<t hangText="ChallengeResponse : Binary [0..1]   " />
<t>
The response to a server 
authentication challenge.
</t>
</list></t>

</section>
<section title="Message: TicketResponse">

<t>
The TicketResponse message returns cryptographic and/or connection
context information to a client.
</t>

<!-- No parameters -->

</section>
<section title="Unbind">

<t>
Requests that a previous device association be deleted.
</t>

</section>
<section title="Message: UnbindRequest">

<t>
Since the ticket identifies the binding to be deleted, the
only thing that the unbind message need specify is that
the device wishes to cancel the binding.
</t>

<!-- No parameters -->

</section>
<section title="Message: UnbindResponse">

<t>
Reports on the success of the unbinding operation.
</t>
<t>
If the server reports success, the client SHOULD delete the
ticket and all information relating to the binding.
</t>
<t>
A service MAY continue to accept a ticket after an unbind request
has been granted but MUST NOT accept such a ticket for
a bind request.
</t>

<!-- No parameters -->

</section>

</section>



    </section>

    <section title="Omnibroker Query Service">
      <!-- Begin section of automatically generated text
Line wrap = 66
   -->

        <section title="Illustrative example">
  <t>
[For illustrative purposes, all the examples in this section
are shown using the Web Services Transport binding.  
Examples of other transport bindgins are shown in  
section [TBS].]
  </t>
          <t>
     The Alice of the previous example uses her Web browser to
 access the URL www.example.com://www.example.com/. Assuming this
   was done while
 the prior binding was still active (i.e. before the UnbindRequest
 message was sent), the Web browser would send a
  QueryConnectRequest  
 request to obtain the best connection parameters for the  
 http protocol at  
 www.example.com:
  </t>

          <figure>
            <artwork>
<![CDATA[Post / HTTP/1.1
Host: example.com
Cache-Control: no-store
Content-Type: Application/json;charset=UTF-8
Content-Length: 131
Content-Integrity:
  mac=BfpMWTx5yhGuwQXhTZtGSHDuPzvgdjYLDS0Ko0vbYNY=;
  ticket=6JhkobO5VTxwwMIn2waC0+6tMoLL+vD8XmFM2oUzqFrDFVpeN9+AxdBQR/
    KOgl5hXCJYJpKo4wQgUTV3E/QnxGcHHc2aVSiWTcna88s84sQ=

{
  "QueryConnectRequest": {
    "Identifier": {
      "Name": "http",
      "Service": "www.example.com",
      "Port": 80}}}]]>
            </artwork>
          </figure>

<t>
The service responds with an ordered list of possible connections.
In this case the site is accessible via plain TCP transport or with
TLS. Since TLS is the preferred protocol, that connection is
listed first.
</t>
          <figure>
            <artwork>
<![CDATA[HTTP/1.1 200  
Content-Type: application/json;charset=UTF-8
Content-Length: 347
Content-Integrity:
  mac=bgDFDBgfnmvE66ma7B+7XZ3sho49JWgU0V+fdBdfqPI=;
  ticket=6JhkobO5VTxwwMIn2waC0+6tMoLL+vD8XmFM2oUzqFrDFVpeN9+AxdBQR/
    KOgl5hXCJYJpKo4wQgUTV3E/QnxGcHHc2aVSiWTcna88s84sQ=

{
  "QueryConnectResponse": {
    "Status": 200,
    "Connection": [{
        "IPAddress": "10.3.2.1",
        "IPPort": 443,
        "Transport": "TLS",
        "TransportPolicy": "TLS=Optional",
        "ProtocolPolicy": "Strict"},
      {
        "IPAddress": "10.3.2.1",
        "IPPort": 80,
        "ProtocolPolicy": "Strict"}]}}]]>
            </artwork>
          </figure>

<t>
Although the QueryConnectResponse returned the hash of a PKIX
certificate considered valid for that connection, the server
returns a different certificate which the client verifies using
the ValidateRequest query.

</t>
          <figure>
            <artwork>
<![CDATA[Post / HTTP/1.1
Host: example.com
Cache-Control: no-store
Content-Type: Application/json;charset=UTF-8
Content-Length: 124
Content-Integrity:
  mac=VBZp1ruh+2F7kZhLxL95Eb9oG1agWyiv9BK7myEJ2WE=;
  ticket=6JhkobO5VTxwwMIn2waC0+6tMoLL+vD8XmFM2oUzqFrDFVpeN9+AxdBQR/
    KOgl5hXCJYJpKo4wQgUTV3E/QnxGcHHc2aVSiWTcna88s84sQ=

{
  "ValidateRequest": {
    "Credential": {
      "Type": "application/x-x509-server-cert",
      "Data": "AAECAwQ="}}}]]>
            </artwork>
          </figure>

<t>
The service validates the certificate according to the  
Omnibroker service policy.  
</t>
          <figure>
            <artwork>
<![CDATA[HTTP/1.1 200  
Content-Type: application/json;charset=UTF-8
Content-Length: 47
Content-Integrity:
  mac=yjp8j5p7P8RbaEK+7924/cEwP2zaHmso3gKfJmCGuzQ=;
  ticket=6JhkobO5VTxwwMIn2waC0+6tMoLL+vD8XmFM2oUzqFrDFVpeN9+AxdBQR/
    KOgl5hXCJYJpKo4wQgUTV3E/QnxGcHHc2aVSiWTcna88s84sQ=

{
  "ValidateResponse": {
    "Status": 200}}]]>
            </artwork>
          </figure>

</section>


<!-- End section of automatically generated text -->

      



<section title="OBPQuery">


<section title="Message: Payload">


<!-- No parameters -->

</section>
<section title="Message: Message">


<!-- No parameters -->

</section>
<section title="Message: Request">

<t>
Every query request contains the following common elements:
</t>

<t> <list style="hanging" hangIndent="6">
<t hangText="Index : Integer [0..1]   " />
<t>
Index used to request a specific response when multiple 
responses are available.
</t>
</list></t>

</section>
<section title="Message: Response">

<t>
Every Query Response contains the following common elements:
</t>

<t> <list style="hanging" hangIndent="6">
<t hangText="Status : Integer [1..1]   " />
<t>
Status return code value
</t>
<t hangText="Index : Integer [0..1]   " />
<t>
Index of the current response.
</t>
<t hangText="Count : Integer [0..1]   " />
<t>
Number of responses available.
</t>
</list></t>

</section>
<section title="Structure: Identifier">

<t>
Specifies an Internet service by means of a DNS address and either a
DNS service prefix, an IP port number or both. An Internet peer 
connection MAY be specified by additionally specifying an account.
</t>

<t> <list style="hanging" hangIndent="6">
<t hangText="Name : Name [1..1]   " />
<t>
The DNS name of the service to connect to.
</t>
<t>
Internationalized DNS names MUST be encoded in punycode
encoding.
</t>
<t hangText="Account : Label [0..1]   " />
<t>
Identifies the account to connect to in the case that a peer connection
is to be established.
</t>
<t hangText="Service : Name [0..1]   " />
<t>
The DNS service prefix defined for use with DNS records that
take a service prefix including SRV.
</t>
<t hangText="Port : Integer [0..1]   " />
<t>
IP Port number.
</t>
<t>
A service identifier MUST specify either a service or a port or both.						
</t>
</list></t>

</section>
<section title="Structure: Connection">


<t> <list style="hanging" hangIndent="6">
<t hangText="IPVersion : Integer [0..1]   " />
<t>
Contains the IP version field. If absent, IPv4 is assumed.
</t>
<t hangText="IPProtocol : Integer [0..1]   " />
<t>
Contains the IP protocol field. If absent, TCP is assumed.
</t>
<t hangText="IPAddress : Binary [0..1]   " />
<t>
IP address in network byte order. This will normally be an 
IPv4 (32 bit) or IPv6 (128 bit) address.
</t>
<t hangText="IPPort : Integer [0..1]   " />
<t>
IP port. 1-65535
</t>
<t hangText="TransportPolicy : String [0..1]   " />
<t>
Transport security policy as specified in [TBS]
</t>
<t hangText="ProtocolPolicy : String [0..1]   " />
<t>
Application security policy specification as specified by 
the application protocol.
</t>
<t hangText="Advice : Advice [0..1]   " />
<t>
Additional information that a service MAY return to support
a service connection identification. 
</t>
</list></t>

</section>
<section title="Structure: Advice">

<t>
Additional information that a service MAY return to support
a service connection identification. For example, DNSSEC 
signatures chains, SAML assertions, DANE records, 
Certificate Transparency proof chains, etc.
</t>

<t> <list style="hanging" hangIndent="6">
<t hangText="Type : Label [0..1]   " />
<t>
The IANA MIME type of the content type
</t>
<t hangText="Data : Binary [0..1]   " />
<t>
The advice data.
</t>
</list></t>

</section>
<section title="Structure: Service">

<t>
Describes a service connection
</t>

<t> <list style="hanging" hangIndent="6">
<t hangText="Identifier : Identifier [0..Many]   " />
<t>
Internet addresses to which the service is to be bound.
</t>
<t hangText="Connection : Connection [0..1]   " />
<t>
Service connection parameters.
</t>
</list></t>

</section>
<section title="QueryConnect">

<t>
Requests a connection context to connect to a specified Internet service
or peer.
</t>

</section>
<section title="Message: QueryConnectRequest">

<t>
Specifies the Internet
service or peer that a connection is to be established to and the
acceptable security policies.
</t>

<t> <list style="hanging" hangIndent="6">
<t hangText="Identifier : Identifier [0..1]   " />
<t>
Identifies the service or peer to which a connection is 
requested.
</t>
<t hangText="Policy : Label [0..Many]   " />
<t>
Acceptable credential validation policy.
</t>
<t hangText="ProveIt : Boolean [0..1]   " />
<t>
If set the broker SHOULD send advice to permit the client to
validate the proposed connection context.
</t>
</list></t>

</section>
<section title="Message: QueryConnectResponse">

<t>
Returns one or more connection contexts in response to a 
QueryConnectRequest Message.
</t>

<t> <list style="hanging" hangIndent="6">
<t hangText="Connection : Connection [0..Many]   " />
<t>
An ordered list of connection contexts with the preferred
connection context listed first.
</t>
<t hangText="Advice : Advice [0..1]   " />
<t>
Proof information to support the proposed connection context.
</t>
<t hangText="Policy : Label [0..Many]   " />
<t>
Policy under which the credentials have been verified.	
</t>
</list></t>

</section>
<section title="Advertise">

<t>
Advises a broker that one or more Internet services are 
being offered with particular attributes.
</t>

</section>
<section title="Message: AdvertiseRequest">

<t>
Specifies the connection(s) to be established.
</t>
<t>
The attributes required depend on the infrastructure(s) that the 
broker is capable of registering the service with.
</t>

<t> <list style="hanging" hangIndent="6">
<t hangText="Service : Service [0..Many]   " />
<t>
Describes a connection to be established.
</t>
</list></t>

</section>
<section title="Message: AdvertiseResponse">

<t>
Specifies the connection(s)
</t>

<t> <list style="hanging" hangIndent="6">
<t hangText="Service : Service [0..Many]   " />
<t>
Describes a connection that was established.
</t>
</list></t>

</section>
<section title="Validate">

<t>
The Validate query requests validation of credentials
presented to establish a connection. For example credentials
presented by a server in the process of setting up a 
TLS session.
</t>

</section>
<section title="Message: ValidateRequest">

<t>
Specifies the credentials to be validated and the purpose
for which they are to be used.
</t>

<t> <list style="hanging" hangIndent="6">
<t hangText="Service : Service [0..1]   " />
<t>
Describes the service for which the credentials 
are presented for access.
</t>
<t hangText="Credential : Credential [0..1]   " />
<t>
List of credentials for which validation is requested.
</t>
<t hangText="Policy : Label [0..Many]   " />
<t>
Policy under which the credentials have been verified.	
</t>
</list></t>

</section>
<section title="Message: ValidateResponse">

<t>
Reports the status of the credential presented.
</t>

<t> <list style="hanging" hangIndent="6">
<t hangText="Policy : Label [0..Many]   " />
<t>
Policy under which the credentials have been verified.	
</t>
</list></t>

</section>
<section title="QueryCredentialPassword">

<t>
The QueryCredentialPassword query is used to request a password credential
that the user has previously chosen to store at the broker.
</t>

</section>
<section title="Message: CredentialPasswordRequest">

<t>
Requests a password for the specified account.
</t>

<t> <list style="hanging" hangIndent="6">
<t hangText="Account : String [0..1]   " />
<t>
The account for which a password is requested.
</t>
</list></t>

</section>
<section title="Message: CredentialPasswordResponse">

<t>
Returns a password for the specified account.
</t>

<t> <list style="hanging" hangIndent="6">
<t hangText="Password : String [0..1]   " />
<t>
The requested password.
</t>
</list></t>

</section>

</section>



    </section>
    
    <section title="Mutual Authentication" anchor="MutualAuth">
      <t>
        A Connection Service MAY require that a connection
        request be  
        authenticated. Three authentication mechanisms are
        defined.
      </t>
      <t>
        <list>
          <t>
            PIN Code: The client and server demonstrate mutual
            knowledge of
            a PIN code previously exchanged out of band.
          </t>
          <t>
            Established Key: The client and server demonstrate
            knowledge of the
            private key associated with a credential previously  
            established. This MAY be a public key or a symmetric
             key.
          </t>
          <t>
            Out of Band Confirmation: The request for access is  
            forwarded to an out of band confirmation service.
          </t>
        </list>
      </t>
    
      <section title="PIN Authentication" anchor="ChallengeResponse">

        <t>
          [Motivation]
        </t>
        <t>
          Although the PIN value is never exposed on the wire in
           any form,
          the protcol considers the PIN value to be a text
          encoded  
          in UTF8 encoding.
        </t>
        <t>
          [Considerations for PIN character set choice discussed
           in body
          of draft, servers MUST support numeric only, clients
          SHOULD  
          support full Unicode]
        </t>
        <t>
          The PIN Mechanism is a three step process:
        </t>
        <t>
          <list>
            <t>
              The client sends an OpenRequest message to the
              Service containing  
              a challenge value CC.
            </t>
            <t>
              The service returns an OpenResponse message
              containing to the client a server
              challenge value SV and a server response value SR.
            </t>
            <t>
              The client sends a TicketRequest message to the
              service containing
              a client response value CR.
            </t>
          </list>
        </t>
        <t>
          Since no prior authentication key has been
          the  
          OpenRequest and OpenResponse messages are initially
          sent without  
          authentication and authentication values established
          the
          Challenge-Response mechanism.
        </t>
        <t>
          The Challenge values CC,  and SC are cryptographic
          nonces. The nonces  
          SHOULD be generated using an appropriate cryptographic
           random
          source. The nonces MUST be at least as long as 128
          bits, MUST be at least  
          the minimum key size  
          of the authentication algorithm used and MUST NOT more
           than 640 bits  
          in length (640 bits should be enough for anybody).
        </t>
        <t>
          The server response and client response values are
          generated
          using an authentication algorithm selected by the
          server from the
          choices proposed by the client in the OpenRequest
          message.
        </t>
        <t>
          The algorithn chosen may be a MAC algorithm or an  
          encrypt-with-authentication (EWA) algorithm. If an EWA
           is specified,  
          the encrypted data is discarded and only the
          authentication  
          value is used in its place.
        </t>
        <t>
          Let A(d,k) be the authentication value obtained by
          applying the  
          authentication algorithm with key k to data d.
        </t>
        <t>
          To create the Server Response value, the UTF8 encoding
           of the
          PIN value 'P' is  
          first converted into a symmetric key KPC by using the
           Client
          challenge value as the key
          truncating if necessary and then applied to the
          of the
          OpenRequest message:
        </t>
        <t>
          KPC = A (PIN, CC)
          SR = A (Secret + SC + OpenRequest, KPC)
        </t>
        <t>
          In the Web Service Binding, the Payload of the message
           is the  
          HTTP Body as presented on the wire. The Secret and
          Server  
          Challenge are presented in their
          binary format and the '+' operator stands for simple
          concatenation
          of the binary sequences.
        </t>
        <t>
          This protocol construction ensures that the party
          constructing
          SR:
        </t>
        <t>
          <list>
            <t>
              Knows the PIN code value (through the construction
               of KPC).
            </t>
            <t>
              Is responding to the Open Request Message (SR
              depends on  
              OpenRequest).
            </t>
            <t>
              Has knowlege of the secret key which MUST be used
               to  
              authenticate the following
              TicketRequest/TicketResponse
              interaction that will establish the actual
              connection.
            </t>
            <t>
              Does not provide an oracle the PIN value. That is,
               the protocol  
              does not provide a service that reveals the (since
               the value SR
              includes the value SC which is a random nonce
              generated
              by the server and cannot be predicted by the
              client).
            </t>
          </list>
        </t>

        <t>
          To create the Client Response value, secret key is
          applied  
          to the PIN value and server Challenge:
        </t>
        <t>
          CR = A (PIN + SC + OpenRequest, Secret)
        </t>
                <t>
          Note that the server can calculate the value of the
          Client Response
          token at the time that it generates the Server
          Challenge.
          This minimizes the amount of state that needs to be
          carried from  
          one request to the next in the Ticket value when using
           the stateless
          server implementation described in section <xref target="stateless" />
        </t>
        <t>
          This protocol construction ensures that the
          of CR
        </t>
        <t>
          <list>
            <t>
              Knows the PIN value.
            </t>
            <t>
              Is respoding to the OpenResponse generated by the
               server.
            </t>
          </list>
        </t>
        <t>
          Note that while disclosure of an oracle for the PIN
          value is a  
          concern in the  
          construction of CR, this is not the case in the
          construction of  
          SR since the client has already demonstrated knowledge
           of the  
          PIN value.
        </t>

        </section>

        <section title="Example: Latin PIN Code">
          <t>
            The Connection Request example of section  
            <xref target="ConnectionRequestExample" />
            demonstrates the use
            of an alphanumeric PIN code using the Latin alphabet.
          </t>
          <t>
            The PIN code is [] and the authentication algorithm
             is [].
            The value KP is thus:
          </t>
          <t>
            [TBS]
          </t>
          <t>
            The data over which the hash value is calulated is
            Secret + SC + OpenRequest:
          </t>
          <t>
            [TBS]
          </t>
          <t>
            Applying the derrived key to the data produces the
            server  
            response:
          </t>
          <t>
            The data for the client response is PIN + SC:
          </t>
          <t>
            [TBS]
          </t>
          <t>
            Applying the secret key to the data produces the
            client
            response:
          </t>
          <t>
            [TBS]
          </t>
        </section>
        <section title="Example: Cyrillic PIN Code">
          <t>
            If the PIN code in the earlier example was [] the
            value KP would be:
          </t>
          <t>
            [TBS]
          </t>           
          <t>
            The Server Response would be:
          </t>
          <t>
            [TBS]
          </t>
          <t>
            The rest of the protocol would then continue as
            before.
          </t>
        </section>
      <section title="Stateless server" anchor="stateless">
        <t>
          The protocol is designed to permit but not require a
          stateless
          implementation by the server using the Ticket value
          generated by the  
          server to pass state from the first server transaction
           to the
          second.
        </t>
        <t>
          In the example shown in <xref target="ConnectionRequestExample" />,  
        the server generates a 'temporary ticket' containing the  
        following information:
        </t>

        <t>
          If a server uses the Ticket to transmit state in this
           way it
          MUST protect the confidentiality of the ticket using a
           strong
          means of encryption and authentication.
         </t>
      </section>
      <section title="Established Key" anchor="PublicKeyAuth">
        <t>
          The Established Key mechanism is used when the parties
           have
          an existing shared key or public key credential.
        </t>
        <t>
          The  
          [Open request open response are authenticated under the
          respective keys]
        </t>
        <t>
          SR=CC, CR=SC
        </t>
      </section>
      <section title="Out of Band Confirmation" anchor="OOBConfirmation">
        <t>
          The Out Of Band Confirmation mechanism is a three step  
          process in which:
        </t>
        <t>
          <list>
            <t>
              The client makes an OpenRequest message to the
              service
              and obtains an OpenResponse message.
            </t>
            <t>
              The service is informed that the service has been
              authorized through an out of band process.
            </t>
            <t>
              The client makes a TicketRequest to the service
              and obtains a TicketResponse message to complete  
              the exchange.
            </t>
          </list>
        </t>
        <t>
          Since no prior authentication key has been
          the  
          OpenRequest and OpenResponse messages are sent without  
          authentication.
        </t>
        <t>
          The principal concern in the Out Of Band Confirmation  
          mechanism is ensuring that the party authorizing the
          request is able to identify which party originated
          the request they are attempting to identify.
        </t>
        <t>
          If a device has the ability to display an image it
          MAY set the HasDisplay=true in the OpenRequest message.
          If the broker recieves an OpenRequest with the
          HasDisplay
          value set to true, the OpenResponse MAY contain one or
           more
          VerificationImage entries specifying image data that
          is
          to be displayed to the user by both the client and the
          confirmation interface.
        </t>
        <t>
          Before confirming the request, the user SHOULD verify  
          that the two images are the same and reject the request
          in the case that they are not.
        </t>
        <t>
          Many devices do not have a display capability, in
          particular
          an embedded device such as a network switch or a
          thermostat.
          In this case the device MAY be identified by means of
           the
          information provided in  
          DeviceID, DeviceURI, DeviceImage and DeviceName.
        </t>
      </section>
    </section>


    <section title="Transport Bindings">
      <t>
        To achieve an optimal balance of efficiency and availability,
        three transport bindings are defined:
      </t>
      <t>
        <list>
          <t hangText="HTTP over TLS">Supports all forms of OBP
          transaction in all network environments.</t>
          <t hangText="DNS Tunnelling">Provides efficient support for a subset
          of OBP query transactions that is accessible in most network
          environments.</t>
          <t hangText="UDP">
            Provides efficient support for all OBP query transactions 
            and is accessible in most network environments.
          </t>
        </list>
      </t>
      <t>
        Support for the HTTP over TLS binding is REQUIRED.
      </t>
      <t>
        An OBP message consists of three parts:
        <list style="hanging">
          <t hangText="Ticket [As necessary]">
            If specified, identifies the cryptographic key and algorithm parameters to be used
            to secure the message payload.
          </t>
          <t hangText="Payload [Required]">
            If the ticket context does not specify use of an encryption algorithm,
            contains the message data. Otherwise contains the 
            message data encrypted under the 
            encryption algorithm and key specified in the ticket context.
          </t>
          <t hangText="Authenticator [Optional]">
            If the ticket context specifies use of a Message Authentication 
            Code (MAC), contains the MAC value calculated over the payload data
            using the authentication key bound to the ticket.
          </t>
        </list>
      </t>
      <t>
        Note that although each of the transport bindings defined in this specification
        entail the use of a JSON encoding for the message data, this is not a 
        necessary requirement for a transport binding. 
      </t>


      <section title="HTTP over TLS">
        <t>
          OBP requests and responses are mapped to HTTP POST requests
          and responses respectively. Java Script Object Notation (JSON)
          encoding is used to encode requests and responses.
        </t>
        <section title="Message Encapsulation">
          <t>
            Requests and responses are mapped to HTTP POST transactions. 
            The content of the HTTP message is the message payload.
            The Content-Type
            MUST be specified as application/json. The Character set MUST
            be specified as UTF-8.
          </t>
          <t>
            The Ticket and Authenticator are specified using the Integrity
            header as follows:
          </t>
          <t>
            Integrity: &lt;base64 (authenticator)&gt; ; ticket=&lt;base64 (ticket)&gt;
          </t>
        </section>     
        <section title="Example">
          <t>
            [To be generated from spec]
          </t>
        </section>
      </section>
      <section title="DNS Tunnel">
        <t>
          The DNS Tunnel mode of operation makes use of DNS TXT resource record
          requests and responses to tunnel OBP Query requests. Due to the constraints
          of this particular mode of operation, use of this transport is in
          practice limited to supporting transactions that can be
          expressed within 500 bytes. These include the QueryConnect
          and ValidateRequest interactions.
        </t>
        <section title="Request">
          <t>Requests are mapped to DNS TXT queries. The request is mapped onto
          the DNS name portion of the query by encoding the Ticket, Authenticator 
          and JSON encoded Payload using Base32 encoding and appending the result to the
          service prefix to create a DNS name as follows:
        </t>
          
            <t>
              &lt;base32(payload)&gt;.&lt;base32(authenticator)&gt;.&lt;base32(ticket)&gt;.Suffix
                
              </t>
          <t>
            The payload MAY be split across multiple DNS labels at any point.
          </t>
        </section>
        <section title="Response">
          <t>
            Responses are mapped to DNS TXT records by encoding the Authenticator
            and JSON encoded Payload using Base64 encoding and cocatenating the result
            with a periods as a separator as follows:
          </t>
        <t>
          &lt;base32(payload)&gt;.&lt;base32(authenticator)&gt;
        </t>
          
        </section>
        <section title="Example">
          <t>
            [To be generated from spec]
          </t>
        </section>
      </section>
      <section title="UDP">
        <t>
          The UDP transport MAY be used for transactions where the request 
          fits into a single UDP packet and the response can be accomadated in
          16 UDP packets.
          As with the Web Service Binding, Java Script Object Notation (JSON)
          encoding is used to encode requests and responses.
        </t>
        <section title="Request">
          <t>The request consists of four message segments containing a Header, 
          Ticket, Payload and Authenticator. Each message segment begins with a 
          two byte field that specified the length of the following data segment
          in network byte order. The Payload is encoded in JSON encoding and the
          remaining fields as binary data without additional encoding.
        </t>
          <t>
            The header field for this version of the protocol (1.0) contains two 
            bytes that specify the Major and Minor version number of the transport 
            protocol being 1 and 0 respectively. Future versions of the transport 
            protocol MAY specify additional data fields.
          </t>
          <t>
            [TBS diagram]
          </t>          
        </section>
        <section title="Response">
          <t>The response consists of a sequence of packets. Each packet consists 
          of a header section and a data section.</t>
          <t>
            The header section consists of a two byte length field followed by two 
            bytes that speciofy the Major and Minor version number of the transport 
            protocol (1 and 0), two bytes that specify the frame number
            and the total number of frames and two bytes that specify the message 
            identifier.
          </t>
          <t>
            [TBS diagram]
          </t>
          <t>
            [Question, should the authenticator be over the whole message 
            or should each packet have its own authenticator?]
          </t>
        </section>
        <section title="Example">
          <t>
            [To be generated from spec]
          </t>
        </section>
      </section>
    </section>
    <section title="Acknowledgements">
      <t>
        [List of contributors]
      </t>
    </section>
    <section title="Security Considerations">

      <section title="Denial of Service">
      </section>
      <section title="Breach of Trust">
      </section>
      <section title="Coercion">
      </section>

    </section>
    <section title="To do">
      <t>

        <list>
          <t>
            The specification should define and use a JSON security object.
          </t>
          <t>Formatting of the abstract data items needs to be improved</t>
          <t>
            Need to specify the UDP transport binding
          </t>
          <t>
            Should specify how each data item is represented in JSON format 
            somewhere. This is obvious for some of the data types but needs 
            to be fully specified for things like DateTime.
          </t>
          <t>
            Run the code to produce proper examples.
          </t>
          <t>
            Write a tool to transclude the example and other xml data into 
            the document source.
          </t>
          <t>
            Fully document the API section.
          </t>
        </list>
      </t>
    </section>
    <section title="For discussion.">
      <t>

        <list>
          <t>
            Should the specification use the form urlencoded convention like
            OAUTH does?
          </t>
          <t>How should responses be cryptographically linked to requests?</t>
          <t>

          </t>
        </list>
      </t>
    </section>
    <section title="IANA Considerations">
      <t>
        [TBS list out all the code points that require an IANA
        registration]
      </t>
    </section>

  </middle>



  <back>


    <references title="Normative References">
      &RFC1035;
      &RFC2119;
      &RFC4366;

      <reference anchor="X.509">
        <front>
          <title>
            ITU-T Recommendation X.509 (11/2008): Information
            technology - Open systems interconnection - The
            Directory: Public-key and attribute certificate
            frameworks
          </title>
          <author>
            <organization>
              International Telecommunication Union
            </organization>
          </author>
          <date month="November" year="2008" />
        </front>
        <seriesInfo name="ITU-T Recommendation" value="X.509" />
        <format type="HTML" target="http://www.itu.int/itu-t/recommendations/rec.aspx?rec=X.509" />
      </reference>
      <reference anchor="X.680">
        <front>
          <title>
            ITU-T Recommendation X.680 (11/2008): Information
            technology - Abstract Syntax Notation One (ASN.1):
            Specification of basic notation
          </title>
          <author>
            <organization>
              International Telecommunication Union
            </organization>
          </author>
          <date month="November" year="2008" />
        </front>
        <seriesInfo name="ITU-T Recommendation" value="X.680" />
        <format type="HTML" target="http://www.itu.int/itu-t/recommendations/rec.aspx?rec=X.680" />
      </reference>

    </references>
    <!--<references title="Non Normative References">

        </references>-->

    <section title="Example Data.">
      <t>

      </t>
      <section title="Ticket A">
        <t>

        </t>
      </section>
      <section title="Ticket B">
        <t>

        </t>
      </section>
    </section>

  </back>
</rfc>