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Versions: 00 01 02 03 04 05 06 07 08 09 10 11 RFC 5019

 PKIX Working Group                                           A. Deacon
 Internet Draft                                                VeriSign
 Category: Informational                                       R. Hurst
 Document: draft-ietf-pkix-lightweight-ocsp-profile-01.txt    Microsoft
 Expires: April 2005                                       October 2004
                         Lightweight OCSP Profile
                       for High Volume Environments
 Status of this Memo
   By submitting this Internet-Draft, I certify that any applicable
   patent or other IPR claims of which I am aware have been disclosed,
   or will be disclosed, and any of which I become aware will be
   disclosed, in accordance with RFC 3668.
   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as
   Internet-Drafts are draft documents valid for a maximum of six
   months and may be updated, replaced, or obsoleted by other documents
   at any time.  It is inappropriate to use Internet-Drafts as
   reference material or to cite them other than a "work in progress."
   The list of current Internet-Drafts can be accessed at
   The list of Internet-Draft Shadow Directories can be accessed at
   This specification defines a profile of the Online Certificate
   Status Protocol (OCSP) that addresses the scalability issues
   inherent when using OCSP in large scale (high volume) PKI
   environments and/or PKI environments that require a lightweight
   solution to minimize bandwidth and client side processing.
 Table of Contents
   1. OCSP Message Profile...........................................3
       1.1 OCSP Request Profile......................................3
       1.1.1 OCSPRequest Structure...................................3
       1.1.2 Signed OCSPRequests.....................................4
       1.2 OCSP Response Profile.....................................4
       1.2.1 OCSPResponse Structure..................................4
       1.2.2 Signed OCSPResponses....................................5
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       1.2.3 OCSPResponseStatus Values...............................5
       1.2.4 thisUpdate, nextUpdate and producedAt...................6
   2. Client Behavior................................................6
       2.1 OCSP Responder Discovery..................................6
       2.2 Sending an OCSP Request...................................6
       2.3 OCSP response status processing...........................7
   3. Ensuring an OCSPResponse is Fresh..............................7
   4. Transport Profile..............................................8
   5. Caching Recommendations........................................9
       5.1 Caching at the Client.....................................9
       5.2 HTTP Proxies..............................................9
       5.3 Caching at Servers.......................................11
   6. Security Considerations.......................................11
       6.1 Replay attacks...........................................11
       6.2 Man-in-the-middle attacks................................12
       6.3 Impersonation attacks....................................12
       6.4 Denial of service attacks................................12
       6.5 Modification of HTTP Headers.............................13
   7. Acknowledgements..............................................13
   8. References....................................................13
       8.1 Normative................................................13
       8.2 Informative..............................................14
   9. Author's Addresses............................................14
   Appendix A. Useful Response Extensions...........................14
       Appendix A.1. nextPublish Response Extension.................14
   Appendix B.  Example OCSP Messages...............................15
       Appendix B.1: OCSP Request...................................15
       Appendix B.2: OCSP Response..................................15
   The Online Certificate Status Protocol [OCSP] specifies a mechanism
   used to determine the status of digital certificates, without
   requiring CRL's.  Since its definition in 1999, it has been deployed
   in a variety of environments and has proven to be a useful
   certificate status checking mechanism.
   To date, many OCSP deployments have been used to ensure timely and
   secure certificate status information for high-value electronic
   transactions or highly sensitive information, such as in the banking
   and financial environments.  As such, the requirement for an OCSP
   responder to respond in "real time" (i.e. generating a new OCSP
   response for each OCSP request) has been important.  In addition,
   these deployments have operated in environments where bandwidth
   usage is not an issue, and have run on client and server systems
   where processing power is not constrained.
   As the use of PKI continues to grow and move into diverse
   environments, so does the need for a scalable and cost effective
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   certificate status mechanism.  Although OCSP  as currently defined
   and deployed meets the need of small to medium sized PKI's which
   operate on powerful systems on wired networks, there is a limit as
   to how these OCSP deployments scale from both a performance and cost
   perspective.  Mobile environments, where network bandwidth is at a
   premium and client side devices are constrained from a processing
   point of view, require the careful use of OCSP to minimize bandwidth
   usage and client side processing complexity.
   Similarly, as PKI continues to be deployed into environments where
   millions if not hundreds of millions of certificates have been
   issued and an equal number of users (also known as relying parties)
   have the need to ensure that the certificate they are relying upon
   have not been revoked, it is important that OCSP is used in such a
   way that ensures the load on OCSP responders and the network
   infrastructure required to host those responders is kept to a
   This document addresses the scalability issues inherent when using
   OCSP in PKI environments described above by defining an message
   profile and OCSP client and responder behavior that will permit:
   1) OCSP response pre-production and distribution
   2) Reduced OCSP message size to lower bandwidth usage
   3) Response message caching both in the network and on the client
   It is intended that the normative requirements defined in this
   profile apply to OCSP clients and OCSP responders operating in very
   large scale (high volume) PKI environments or PKI environments that
   require a lightweight solution to minimize bandwidth and client side
   processing power (or both), as described above.
    1.       OCSP Message Profile
   This section defines a subset of OCSPRequest and OCSPResponse
   functionality as defined in [OCSP].
    1.1        OCSP Request Profile
    1.1.1 OCSPRequest Structure
   OCSPRequests conformant to this profile MUST include only one
   Request in the OCSPRequest.RequestList structure.
   Clients MUST use SHA1 as the hashing algorithm for the
   CertID.issuerNameHash and the CertID.issuerKeyHash values.
   Clients MUST NOT include the singleRequestExtensions structure.
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   Clients SHOULD NOT include the requestExtensions structure.  If a
   requestExtensions structure is included, this profile RECOMMENDS
   that it contain only the nonce extension (id-pkix-ocsp-nonce).  See
   Section 3 for issues concerning the use of a nonce in high volume
   OCSP environments.
    1.1.2 Signed OCSPRequests
   Clients SHOULD NOT create or send signed OCSPRequests.  Responders
   MAY ignore the signature on OCSPRequests.
   If the OCSPRequest is signed, the client SHALL specify its name in
   the OCSPRequest.requestorName field, otherwise clients SHOULD NOT
   include the requestorName field in the OCSPRequest. OCSP servers
   MUST be prepared to receive unsigned OCSP requests that contains the
   requestorName field, but must realize that the provided value is not
   Note: The suggested use of unsigned requests in this environment
   does not enable a responder to determine the authenticity of
   incoming request.  Thus, access to the responder is implicitly given
   to any relying party.
    1.2        OCSP Response Profile
    1.2.1 OCSPResponse Structure
   Responders MUST generate a BasicOCSPResponse as identified by the
   id-pkix-ocsp-basic OID. Clients MUST be able to parse and accept a
   BasicOCSPResponse.  OCSPResponses conformant to this profile SHOULD
   include only one SingleResponse in the ResponseData.responses
   structure, but MAY include additional SingleResponse elements if
   necessary to improve response pre-generation performance or cache
   The responder SHOULD NOT include responseExtensions. Clients MUST
   NOT fail if they encounter non-critical responseExtensions in the
   In the case a responder does not have the ability to respond to an
   OCSP request containing a nonce, such as if it only has the ability
   to use pre-produced responses, it SHOULD return a response that does
   not include a nonce. Clients SHOULD attempt to accept a response
   even if the response does not include a nonce.  See Section 3 for
   details on validating responses that do not contain a nonce.  See
   also Section 6 for relevant security considerations.
   Responders that do not have the ability to respond to OCSP requests
   that contain a nonce MAY forward the request to an OCSP responder
   capable of doing so.
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   The responder MAY include the singleResponse extensions structure.
    1.2.2 Signed OCSPResponses
   Responders MUST use the sha1WithRSAEncryption signature algorithm
   when signing the OCSPResponse.  Clients MUST validate the signature
   on the returned OCSPResponse.
   <<Editors Note: Need to determine best way to future-proof this
   draft with the new sha*WithRSAEncryption signature algorithms.
   Options are to either depend on the next version of OCSP and update
   when available or simply define that clients and servers MAY use the
   more modern algs.>>
   If the response is signed by a delegate of the issuing CA the
   responder certificate MUST be referenced in the
   BasicOCSPResponse.certs structure.
   The responder's certificate SHOULD have a validity window greater
   than or equal to the validity window of the responses it issues.
   It is RECOMMENDED that the OCSP responder's certificate contain the
   id-ocsp-nocheck EKU OID to indicate to the client that it need not
   check its status.  In addition, it is RECOMMENDED that neither an
   OCSP authorityInfoAccess (AIA) extension nor CDP extension be
   included in the the OCSP responder's certificate.  Accordingly, the
   responder's signing certificate SHOULD be relatively short-lived and
   rolled over regularly.
   Clients MUST be able to identify OCSP responder certificates using
   both the byName and byKey ResponseData.ResponderID choices.
   Responders MAY use byKey to further reduce the size of the response
   in scenarios where reducing bandwidth is an issue.
    1.2.3 OCSPResponseStatus Values
   As long as the responder has records for a particular certificate,
   an OCSPResponseStatus of "successful" will be returned.
   In order to ensure the database of revocation information does not
   grow unbounded over time, the responder MAY remove the status
   records of expired certificates.
   OCSP responders that pre-produce and distribute OCSP responses in
   advance do not have the ability to properly respond with a signed
   "sucessful" yet "unknown" response as it is impossible to
   pre-produce and sign a response for the set of all possible
   "unknown" CertID's in advance.  Because of this, the responder will
   return an OCSPResponseStatus of "unauthorized" when processing
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   requests for which it is not capable of responding authoritatively.
   This includes the scenario where a responder has removed the records
   of expired certificates from its database.
    1.2.4 thisUpdate, nextUpdate and producedAt
   When pre-producing OCSPResponse messages, the responder MUST set the
   thisUpdate, nextUpdate and producedAt times as follows:
   thisUpdate    The time at which the status being indicated is
                  known to be correct.
   nextUpdate    The time at or before which newer information
                  will be available about the status of the
                  certificate.  Responders MUST always include
                  this value to aid in response caching.  See
                  Section 5 for additional information on
   producedAt    The time at which the OCSP response is signed.
   Note: In many cases the value of thisUpdate and producedAt will be
   the same.
   For the purposes of this profile, GeneralizedTime values such as
   thisUpdate, nextUpdate and producedAt MUST be expressed Greenwich
   Mean Time (Zulu) and MUST include seconds (i.e.,times are
   YYYYMMDDHHMMSSZ), even where the number of seconds is zero.
   GeneralizedTime values MUST NOT include fractional seconds.
   2.      Client Behavior
    2.1        OCSP Responder Discovery
   Clients MUST support the authorityInfoAccess extension as defined in
   [PKIX] and MUST recognize the id-ad-ocsp access method.  This
   enables CAs to inform clients how they can contact the OCSP service.
   In the case where a client is checking the status of a certificate
   that contains both an authorityInformationAccess (AIA) extension
   pointing to a OCSP responder and a cRLDistributionPoints extension
   pointing to a CRL, the client MUST contact the OCSP responder first.
   Clients MAY attempt to retrieve the CRL if and only if no
   OCSPResponse is received from the responder.
    2.2        Sending an OCSP Request
   To avoid needless network traffic, applications MUST verify the
   signature of signed data before asking an OCSP client to check the
   status of certificates used to verify the data. If the signature is
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   invalid or the application is not able to verify it, an OCSP check
   MUST NOT be requested.
   Similarly, applications MUST validate the signature on certificates
   and its chain, before asking an OCSP client to check the status of
   the certificate. If the certificate signature is invalid or the
   application is not able to verify it, an OCSP check MUST NOT be
   requested.  Clients SHOULD NOT request the status of expired
    2.3        OCSP response status processing
   OCSP response status 'good': The client MUST inform the calling
   application that the certificate has not been revoked.
   The client SHOULD NOT accept an OCSP response that indicates (in the
   nextUpdate field) that a newer response is available.  See Section
   5.1 for details on client caching behavior
   OCSP response status 'revoked': The client MUST inform the calling
   application that the signature is untrusted and abort any further
   processing of the signed data.
   OCSP response status 'unknown': The client MUST inform the calling
   application about the unknown certificate status. This profile
   RECOMMENDS calling applications to warn the user about the unknown
   certificate status and give the user the option to continue or abort
   the processing of the data, with a default option of abort.
   3.      Ensuring an OCSPResponse is Fresh
   In order to ensure a client does not accept an out of date response
   that indicates a 'good' status when in fact there is a more up to
   date response that specifies the status of 'revoked', a client must
   ensure the responses they receive are fresh.
   In general, two mechanisms are available to clients to ensure a
   response is fresh.  The first uses nonces, and the second is based
   on time.  In order for time based mechanisms to work, both clients
   and responders MUST have access to an accurate source of time.
   Because this profile specifies that clients SHOULD NOT include a
   requestExtensions structure in OCSPRequests (See Section 1.1)
   clients MUST be able to determine OCSPResponse freshness based on an
   accurate source of time.  Clients that opt to include a nonce in the
   request MUST NOT reject a corresponding OCSPResponse solely on the
   basis of the non-existent expected nonce, but MUST fall back to
   validating the OCSPResponse based on time.
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   If a client includes a nonce in an OCSPRequest, and receives a nonce
   in the corresponding OCSPResponse it MUST ensure that the nonce
   included in the OCSPRequest matches the nonce received in the
   OCSPRequest.  If the nonces do not match the client MUST reject the
   response as invalid.  Clients that do not include a nonce in the
   request MUST ignore any nonce that may be present in the response.
   If there is no nonce in the OCSPResponse, clients MUST check for the
   existence of the nextUpdate field and MUST ensure the current local
   time falls between the thisUpdate and nextUpdate times.  If the
   nextUpdate field is absent, and there's no other way for the client
   to determine the freshness of the response, the client MUST reject
   the response.
   If the nextUpdate field is present the client MUST ensure that it is
   not earlier than current time.  If the current local time on the
   client is later than the time specified in the nextUpdate field, the
   client MUST reject the response as stale.  Clients MAY allow
   configuration of a small tolerance period for acceptance of
   responses after nextUpdate to handle minor clock differences
   relative to responders and caches.  This tolerance period should be
   no more than a few minutes to avoid introducing increased security
   See the security considerations in Section 6 for additional details
   on replay and man-in-the-middle attacks.
   4.      Transport Profile
   The OCSP responder MUST support requests and responses over HTTP.
   When sending requests that are less than 255 bytes in total (after
   encoding) including the method (http://), server name and base64
   encoded OCSPReqeust structure, clients MUST use the GET method (to
   enable for OCSP response caching). OCSP requests larger than 255
   bytes SHOULD be submitted using the POST method. In all cases,
   clients MUST follow the descriptions in A.1.1 of [OCSP] when
   constructing these messages.
   When constructing a GET message, OCSP clients MUST base64 encode the
   OCSPRequest structure and append it to the URI specified in the AIA
   extension [PKIX].  Clients MUST NOT include CR or LF characters in
   the base64-encoded string.  Clients MUST properly url-encode the
   base64 encoded OCSPRequest, e.g.
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   In response to properly formatted OCSPRequests that are cachable
   (i.e. responses that contain a nextUpdate value), the responder will
   include the binary value of the DER encoding of the OCSPResponse
   preceded by the following HTTP headers.
      content-length=<OCSP response length>
      last-modified: <producedAt HTTP date>
      expires: <nextUpdate HTTP date>
      cache-control: max-age=<n>, public, no-transform, must-revalidate
      date: <current HTTP date>
   See Section 5.2 for details on the use of these headers.
   5.      Caching Recommendations
   The ability to cache OCSP Responses throughout the network is an
   important factor in high volume OCSP deployments.  This section
   discusses the recommended caching behavior of OCSP clients and HTTP
   proxies and the steps that should be taken to minimize the number of
   times that OCSP clients "hit the wire".   In addition the concept of
   including OCSP responses in protocols exchanges (aka stapling or
   piggybacking), such as has been defined in TLS, is also discussed.
    5.1        Caching at the Client
   To minimize bandwidth usage, clients MUST locally cache
   authoritative OCSP responses. (i.e. those who's signature has
   successfully validated and that indicate an OCSPResponseStatus of
   'successful')  Once cached, the client SHOULD NOT send a new OCSP
   request until the nextUpdate time in the cached response.
   Most OCSP clients will send OCSPrequests at or near the nextUpdate
   time (when the cached response expires). To avoid large spikes in
   responder load that might occur when many clients refresh cached
   responses for a popular certificate (e.g. www.bigecommercesite.com),
   clients MAY use a locally derived value (i.e. 48 hours) to specify a
   time period before nextUpdate time when a client might consider
   refreshing its cached response. For example, a client can select a
   random time between "nextUpdate minus locally configured value" and
   "nextUpdate" at which to request a refresh of its cached
    5.2        HTTP Proxies
   The responder SHOULD set the HTTP headers of the OCSP response in
   such a way to allow for the intelligent use of intermediate HTTP
   proxy servers.
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   HTTP Header     Description
   ===========    ====================================================
   date            The date and time at which the OCSP server generated
                   the HTTP response.
   last-modified   This value specifies the date and time at which the
                   OCSP responder last modified the response.  This
                   date and time will be the same as the thisUpdate
                   timestamp in the request itself.
   expires         Specifies how long the response is considered fresh.
                   This date and time will be the same as the
                   nextUpdate timestamp in the OCSP response itself.
   cache-control   Contains a number of caching directives.
                * max-age=<n>- where n is the nextUpdate time
                               minus the time the response is
                               generated (i.e. the Date header)
                               in seconds.
                * public-      makes normally uncachable response
                               cachable by both shared and
                               nonshared caches.
                * no-transform-specifies that a proxy cache cannot
                               change the type, length , or
                               encoding of the object content.
                * must-revalidate-   prevents caches from
                                     intentionally returning stale
   OCSP responders MUST NOT include a Pragma: no-cache or
   Cache-Control: no-store header in all OCSP responses.
   For example, assume that an OCSP response has the following time
   stamp values:
      thisUpdate = May 1, 2003  01:00:00 GMT
      nextUpdate = May 3, 2003 01:00:00 GMT
      productedAt = May 1, 2003 01:00:00 GMT
   and that an OCSP client requests the response on May 2, 2003
   01:00:00 GMT.  In this scenario the HTTP response will look like
      content-type: application/ocsp-response
      content-transfer-encoding: binary
      content-length: <OCSP response length>
      date: Fri, 02 May 2003 01:00:00 GMT
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      last-modified: Thu, 01 May 2003 01:00:00 GMT
      expires: Sat, 03 May 2003 01:00:00 GMT
      cache-control: max-age=86400,public,no-transform,must-revalidate
   If a client encounters an expired response, it may be a result of an
   intermediate proxy caching stale data, as such clients SHOULD resend
   the request specifying that proxies should be bypassed by including
   an appropriate HTTP header in the request (i.e. Pragma: no-cache or
   Cache-Control: no-store).
    5.3        Caching at Servers
   In some scenarios it is advantageous to include OCSP response
   information within the protocol being utilized between the client
   and server.  Including OCSP responses in this manner has a few
   attractive effects.
   First, it allows for the caching of OCSP responses on the server,
   thus lowering the number of hits to the OCSP responder.
   Second, it simplifies the client side OCSP implementation by
   enabling a situation where the client need only the ability to parse
   and recognize OCSP responses.
   Third, it reduces the number of round trips the client needs to make
   in order to validate a certificate.
   Fourth, it enables certificate validation in the event the client is
   not connected to a network and thus eliminates the need for clients
   to establish a new HTTP session with the responder.
   This functionality has been specified as an extension to the TLS
   [TLS] protocol in Section 3.6 [TLSEXT], but can be applied to any
   client-server protocol.
   This profile RECOMMENDS that both TLS clients and servers implement
   the certificate status request extension mechanism for TLS.
   6.      Security Considerations
   The following considerations apply in addition to the security
   consideration addressed in Section 5 of [OCSP]
    6.1        Replay attacks
   Because the use of nonce's in this profile is optional, there is a
   possibility that an out of date OCSP response could be replayed,
   thus causing a client to accept good response when in fact there is
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   a more up to date response that specifies the status of revoked.  In
   order to mitigate this attack, clients MUST have access to an
   accurate source of time and ensure that the OCSP responses they
   receive are sufficiently fresh.
   Required clock accuracy is relative to the validity duration of the
   client's OCSP responses.  A client using responses that are good for
   one hour SHOULD have a clock that is within a few minutes correct
   time, while a client with 24-hour responses SHOULD be within an hour
   of correct time.
   Clients that do not have an accurate source of date and time are
   vulnerable to service disruption due to rejection of fresh OCSP
   responses.  If this problem is not repaired, a client with a
   sufficiently slow clock may also incorrectly accept expired
   responses for currently revoked certificates.
    6.2        Man-in-the-middle attacks
   To mitigate risk associated with this class of attack, the client
   must properly validate the signature on the response.
   The use of signed responses in OCSP serves the purpose to
   authenticate the identity of the OCSP responder that has authority
   to sign request on the CA's behalf.
   Clients MUST ensure that they are communicating with an authorized
   responder by the rules described in [OCSP] Section
    6.3        Impersonation attacks
   The use of signed responses in OCSP serves the purpose to
   authenticate the identity of OCSP Responder.
   Clients must properly validate the signature of the OCSP response
   and the signature(s) on the OCSP response signer certificate to
   ensure an authorized responder created it.
    6.4        Denial of service attacks
   OCSP responders should take measures to prevent or mitigate denial
   of service attacks. In particular OCSP responders should not perform
   an unlimited number of resource intensive operations.
   In the case where client requests are not signed, as specified by
   this profile, OCSP responders should take additional steps to detect
   an attack of this kind.
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   One such technique could be to attempt to match which response to
   send based on the hash of the request, this would protect against
   decode related attacks. However since extensions are supported not
   all requests for the same certificate will be the same as such it
   would also be necessary to support a full decode based lookup. As
   such this technique would only help defend against accidental
    6.5        Modification of HTTP Headers
   Values included in HTTP headers as described in Section 4 and 5, are
   not cryptographically protected, they may be manipulated by an
   attacker.  Clients SHOULD use these values for caching guidance only
   and should ultimately rely on the values present in the signed
   7.      Acknowledgements
   The authors wish to thank Magnus Nystrom Of RSA Security, Inc.,
   Jagjeet Sondh of Vodafone Group R&D and David Engberg of CoreStreet,
   Ltd. for their contributions to this specification.
   8.      References
    8.1        Normative
   [HTTP] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
          Masinter, L., Leach, P. and T. Berners-Lee, "Hypertext
          Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
   [KEYWORDS]Bradner, S., "Key words for use in RFCs to Indicate
          Requirement Levels", BCP 14, RFC 2119, March 1997.
   [OCSP] Myers, M., Ankney, R., Malpani, A., Galperin, S. and
          C. Adams, "Internet X.509 Public Key Infrastructure:
          Online Certificate Status Protocol - OCSP", RFC 2560,
          June 1999.
   [PKIX] Housley, R., Polk, W., Ford, W. and D. Solo, "Internet
          Public Key Infrastructure - Certificate and
          Certificate Revocation List (CRL) Profile", RFC 3280,
          April 2002.
   [TLS]     Dierks, T. and C. Allen, "The TLS Protocol Version
          1.0", RFC 2246, January 1999.
   [TLSEXT]  Blake-Wilson, et. al., "Transport Layer Security (TLS)
          Extensions", RFC 3546, June 2003.
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    8.2        Informative
   [URI]     Berners-Lee, T., Fielding, R. and L. Masinter,
          "Uniform Resource Identifiers (URI): Generic Syntax",
          RFC 2396, August 1998
   [PKIOP]Housley, R. and P. Hoffman, "Internet X.509 Public Key
          Infrastructure - Operation Protocols: FTP and HTTP",
          RFC 2585, May 1999.
   [OCSPMP]  "OCSP Mobile Profile", OpenMobileAlliance,
   9.      Author's Addresses
   Alex Deacon
   VeriSign, Inc.
   487 E. Middlefield Road      Phone:  1-650-426-3478
   Mountain View, CA. USA       Email:  a1ex@verisign.com
   Ryan Hurst
   One Microsoft Way            Phone:  1-425-707-8979
   Redmond, WA. USA             Email:  rmh@microsoft.com
   Appendix A. Useful Response Extensions
    Appendix A.1. nextPublish Response Extension
   Support for this extension is optional. This extension indicates the
   time at which the server will be issuing new information about the
   status of the certificate. If present can be used by the relying
   party to determine when it is acceptable to begin attempts for new
   The time specified in the nextPublish extension SHOULD be before the
   time specified in the nextUpdate field.
   This profile RECOMMENDEDS this value be used by clients to determine
   when it is possible to check for more up to date information.
      id-msft-nextPublish OBJECT IDENTIFIER ::= {}
       nextPublish EXTENSION ::= {
        SYNTAX           nextPublishSyntax
        IDENTIFIED BY    id-msft-nextPublish
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      nextPublishSyntax ::= Time
      Time ::= CHOICE {
         utcTime        UTCTime,
         generalTime    GeneralizedTime
   Appendix B.  Example OCSP Messages
    Appendix B.1: OCSP Request
       SEQUENCE {
         SEQUENCE {
           SEQUENCE {
             SEQUENCE {
               OBJECT IDENTIFIER sha1 (1 3 14 3 2 26)
             OCTET STRING
               C0 FE 02 78 FC 99 18 88 91 B3 F2 12 E9 C7 E1 B2
               1A B7 BF C0
             OCTET STRING
               0D FC 1D F0 A9 E0 F0 1C E7 F2 B2 13 17 7E 6F 8D
               15 7C D4 F6
               6B 26 79 83 A4 9A B7 C2 3D FF 58 E8 81 AA A5 0E
    Appendix B.2: OCSP Response
      [0] {
        SEQUENCE {
          OBJECT IDENTIFIER ocspBasic (1 3 6 1 5 5 7 48 1 1)
          OCTET STRING, encapsulates {
            SEQUENCE {
              SEQUENCE {
                [1] {
                  SEQUENCE {
                    SET {
                      SEQUENCE {
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                        OBJECT IDENTIFIER organizationName (2 5 4 10)
                        PrintableString 'Example, Inc.'
                    SET {
                      SEQUENCE {
                        OBJECT IDENTIFIER
                          organizationalUnitName (2 5 4 11)
                        PrintableString Example Trust Network'
                    SET {
                      SEQUENCE {
                        OBJECT IDENTIFIER
                          organizationalUnitName (2 5 4 11)
                      'Terms of use at https://www.example.com/rpa'
                    SET {
                      SEQUENCE {
                        OBJECT IDENTIFIER commonName (2 5 4 3)
                      'Example Class 3 International Server OCSP'
                GeneralizedTime 11/09/2003 14:55:57 GMT
                SEQUENCE {
                  SEQUENCE {
                    SEQUENCE {
                      SEQUENCE {
                        OBJECT IDENTIFIER sha1 (1 3 14 3 2 26)
                      OCTET STRING
                      C0 FE 02 78 FC 99 18 88 91 B3 F2 12 E9 C7 E1 B2
                      1A B7 BF C0
                      OCTET STRING
                      0D FC 1D F0 A9 E0 F0 1C E7 F2 B2 13 17 7E 6F 8D
                      15 7C D4 F6
                      6B 26 79 83 A4 9A B7 C2 3D FF 58 E8 81 AA A5 0E
                      Error: Object has zero length.
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                    GeneralizedTime 11/09/2003 14:55:57 GMT
              SEQUENCE {
                OBJECT IDENTIFIER
                  sha1withRSAEncryption (1 2 840 113549 1 1 5)
              BIT STRING
                17 C3 A3 0B 87 1A A5 C9 39 D2 1E E4 49 9C 84 48
                DC E7 9A 68 89 77 BE 25 60 97 D9 FB 8C D0 C5 E8
                9B D2 25 F6 52 E9 BA 22 C8 FE C4 B6 B3 9F 1F 71
                58 FC BE 39 DC 9D 4E 85 00 8C F1 A9 92 CD 25 CA
                3C DC B9 61 46 76 87 BD A1 E9 F6 41 E2 B3 D6 7E
                E1 FD A1 5D 2D 08 7C 01 3F 2C 3A 39 60 F1 53 AD
                1E 81 E0 57 55 02 F7 D3 FC 9A F8 CA 09 DA 87 1E
                8A 93 01 58 E0 31 72 A1 4A 05 F7 3E 21 2F D7 93
              [0] {
                SEQUENCE {
                  SEQUENCE {
                    SEQUENCE {
                      [0] {
                        INTEGER 2
                      24 D4 27 7D 62 AC 2D 92 F8 D3 4E B1 A5 19 84 78
                      SEQUENCE {
                        OBJECT IDENTIFIER
                          sha1withRSAEncryption (1 2 840 113549 1 1 5)
                      SEQUENCE {
                        SET {
                          SEQUENCE {
                            OBJECT IDENTIFIER
                              organizationName (2 5 4 10)
                            PrintableString "Example Trust Network'
                        SET {
                          SEQUENCE {
                            OBJECT IDENTIFIER
                              organizationalUnitName (2 5 4 11)
                            PrintableString 'Example, Inc.'
                        SET {
                          SEQUENCE {
                            OBJECT IDENTIFIER
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                              organizationalUnitName (2 5 4 11)
                      'Example International Server CA - Class 3'
                      SEQUENCE {
                        UTCTime 09/07/2002 00:00:00 GMT
                        UTCTime 24/10/2011 23:59:59 GMT
                      SEQUENCE {
                        SET {
                          SEQUENCE {
                            OBJECT IDENTIFIER
                              organizationName (2 5 4 10)
                            PrintableString 'Example, Inc.'
                        SET {
                          SEQUENCE {
                            OBJECT IDENTIFIER
                              organizationalUnitName (2 5 4 11)
                            PrintableString 'Example Trust Network'
                        SET {
                          SEQUENCE {
                            OBJECT IDENTIFIER commonName (2 5 4 3)
                                 'Example OCSP Responder'
                      SEQUENCE {
                        SEQUENCE {
                          OBJECT IDENTIFIER
                            rsaEncryption (1 2 840 113549 1 1 1)
                        BIT STRING, encapsulates {
                          SEQUENCE {
                      00 CF 50 81 96 9A F5 D8 E2 DE 0B CF A3 A6 FB 46
                      3E 88 0F 34 0F 5B 28 93 6D 32 EC D1 D0 0B 9B B4
                      5C 9E 12 F0 22 79 1E 6E 0D C6 39 7E A8 C5 01 A7
                      9F D8 93 D4 48 61 19 28 9A 93 7F ED 2A C4 CA 2C
                      E3 47 0C 49 D6 7E D2 FB BC 2C 08 0D 9C FF 05 E6
                      B0 EC 4B 93 1C AF 8E A9 F3 00 07 09 CF 9B 60 F6
                      ED D1 B9 62 6F F1 A7 D3 61 0A 64 30 93 C9 43 4A
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                        Lightweight OCSP Profile           October 2004
                      0E 3E A3 3E 47 D7 B2 0D B4 65 53 CC 0A FE CF E5
                              [ Another 1 bytes skipped ]
                            INTEGER 65537
                      [3] {
                        SEQUENCE {
                          SEQUENCE {
                            OBJECT IDENTIFIER
                              basicConstraints (2 5 29 19)
                            OCTET STRING, encapsulates {
                              SEQUENCE {}
                          SEQUENCE {
                            OBJECT IDENTIFIER
                              certificatePolicies (2 5 29 32)
                            OCTET STRING, encapsulates {
                              SEQUENCE {
                                SEQUENCE {
                                  OBJECT IDENTIFIER
                                          '2 16 840 1 1 1 7 23 3'
                                  SEQUENCE {
                                    SEQUENCE {
                                      OBJECT IDENTIFIER
                                        cps (1 3 6 1 5 5 7 2 1)
                          SEQUENCE {
                            OBJECT IDENTIFIER extKeyUsage (2 5 29 37)
                            OCTET STRING, encapsulates {
                              SEQUENCE {
                                OBJECT IDENTIFIER
                                  ocspSigning (1 3 6 1 5 5 7 3 9)
                          SEQUENCE {
                            OBJECT IDENTIFIER keyUsage (2 5 29 15)
                            OCTET STRING, encapsulates {
                              BIT STRING 7 unused bits
                                '1'B (bit 0)
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                        Lightweight OCSP Profile           October 2004
                          SEQUENCE {
                            OBJECT IDENTIFIER
                              ocspNoCheck (1 3 6 1 5 5 7 48 1 5)
                            OCTET STRING, encapsulates {
                    SEQUENCE {
                      OBJECT IDENTIFIER
                        sha1withRSAEncryption (1 2 840 113549 1 1 5)
                    BIT STRING
                      91 C2 C6 73 75 63 9A 6E A9 A6 F1 4D 99 F6 63 93
                      83 78 2A DB DE 56 DE 86 B5 9A B5 E7 27 44 35 28
                      2E F3 62 B4 9F 17 9F 2B 21 31 90 00 B0 86 E3 AE
                      B6 2C 72 08 9B B8 9D A3 58 61 A8 01 35 8B 3C 6C
                      6A D4 FF 01 FA E7 25 0D E8 D4 A5 8D 8E DF 3A 39
                      11 DE 8E 7A 41 BC 56 48 98 A5 06 86 64 4E AD 0F
                      5B D1 C7 BB 11 57 45 D4 06 F6 FF 3C 7E C5 78 7B
                      68 C1 B6 71 9D 45 79 1D F7 03 0E 9E 6A 75 24 51
   Full Copyright Statement
   Copyright (C) The Internet Society 2004.  This document is subject
   to the rights, licenses and restrictions contained in BCP 78, and
   except as set forth therein, the authors retain all their rights.
   This document and the information contained herein are provided on
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