Internet Draft A .Deacon Category: Informational VeriSign Document: draft-deacon-lightweight-ocsp-profile-00.txt R. Hurst Expires: May 2004 Microsoft November 2003 Lightweight OCSP Profile for High Volume Environments Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026 [KEYWORDS]. 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. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/1id-abstracts.html The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html Abstract This document defines a lightweight profile of OCSP (RFC 2560) for use in very large PKI environments such as SSL/TLS, code signing and secure messaging. In these environments there exists a large client base (in the 100's of millions) and thus the ability to scale OCSP request handling is very important. Table of Contents Introduction.....................................................2 1. OCSP Message Profile..........................................2 1.1 OCSP Request Profile......................................2 1.1.1 OCSPRequest Structure...................................2 1.1.2 Signed OCSPRequests.....................................3 1.2 OCSP Response Profile.....................................3 1.2.1 OCSPResponse Structure..................................3 1.2.2 Signed OCSPResponses....................................4 1.2.3 OCSPResponseStatus Values...............................4 1.2.4 thisUpdate, nextUpdate and producedAt...................4 Deacon Expires - May 2004 [Page 1] Lightweight OCSP Profile November 2003 2. Ensuring an OCSPResponse is Fresh.............................5 3. Transport Profile.............................................6 4. Caching Recommendations.......................................7 4.1 Caching at the Client.....................................7 4.2 HTTP Proxies..............................................7 4.3 Caching at Servers........................................8 5. Security Considerations.......................................9 5.1 Replay attacks............................................9 5.2 Man-in-the-middle attacks................................10 5.3 Impersonation attacks....................................10 5.4 Denial of service attacks................................10 5.5 Modification of HTTP Headers.............................10 6. Acknowledgements.............................................11 7. References...................................................11 7.1 Normative................................................11 7.2 Informative..............................................11 8. Author's Addresses...........................................12 Appendix A. Useful Response Extensions..........................12 Appendix A.1. nextPublish Response Extension.................12 Appendix B. Example OCSP Messages..............................12 Appendix B.1: OCSP Request...................................12 Appendix B.2: OCSP Response..................................13 Introduction This document addresses the OCSP [OCSP] scalability issues inherent in high volume PKI environments by defining an OCSP message profile 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 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 only include 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. Deacon Expires - May 2004 [Page 2] Lightweight OCSP Profile November 2003 Clients SHOULD NOT include the requestExtensions structure. If a requestExtensions structure is included, this profile RECOMMENDS that it only contain the nonce extension (id-pkix-ocsp-nonce). See Section 2 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 authenticated. 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 only include one SingleResponse in the ResponseData.responses structure, but MAY include additional SingleResponse elements if necessary to improve response pre-generation performance or cache efficiency. The responder SHOULD NOT include responseExtensions. Clients MUST NOT fail if they encounter non-critical responseExtensions in the response. 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 2 for details on validating responses that do not contain a nonce. See also Section 5 for relevant security considerations. Deacon Expires - May 2004 [Page 3] Lightweight OCSP Profile November 2003 Responders that cannot respond to OCSP requests that contain a nonce MAY forward the request to an OCSP responder capable of generating a real-time response. 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. 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 MUST have a validity window greater than or equal to the validity window of the responses it issues. In addition, 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. Accordingly, the responders' 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. The responder will return an OCSPResponseStatus of "unauthorized" when processing requests for which it is not capable of responding authoritatively. 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 Deacon Expires - May 2004 [Page 4] Lightweight OCSP Profile November 2003 will be available about the status of the certificate. Responders MUST always include this value to aid in response caching. See Section 3 for additional information on caching. 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. 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, clients 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. 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. 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. Deacon Expires - May 2004 [Page 5] Lightweight OCSP Profile November 2003 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 risks. See the security considerations in Section 5 for additional details on replay and man-in-the-middle attacks. 3. 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. 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. http://ocsp.example.com/MEowSDBGMEQwQjAKBggqhkiG9w0CBQQQ7sp6GTKpL 2dAdeGaW267owQQqInESWQD0mGeBArSgv%2FBWQIQLJx%2Fg9xF8oySYzol80Mbpg %3D%3D In response to a properly formatted OCSPRequest that do not contain a nonce, the responder will include the binary value of the DER encoding of the OCSPResponse preceded by the following HTTP headers. content-type=application/ocsp-response content-transfer-encoding=binary content-length= last-modified: expires: cache-control: max-age=, public, no-transform, must-revalidate date: See Section 4.2 for details on the use of these headers. Deacon Expires - May 2004 [Page 6] Lightweight OCSP Profile November 2003 4. 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 piggybacking OCSP responses in protocols, such as TLS, is also discussed. 4.1 Caching at the Client To minimize bandwidth usage, clients MUST locally cache authoritative OCSP responses. (i.e. those with an OCSPResponseStatus of ‘successful') Once cached, the client SHOULD NOT send a new OCSP request until the nextUpdate time in the cached response. To ensure a large subset of clients don't request a new OCSPResponse for a popular certificate at the same time thus causing a spike in responder load, the client MAY use a locally configured value to determine when to begin attempting to retrieve more recent revocation information slightly in advance of the nextUpdate period. (See Appendix A.1 for details of how a responder can specify this value to the client.) Clients SHOULD NOT request the status of expired certificates. Clients MUST validate the signature on certificates and SHOULD NOT request the status for certificates with signatures that cannot be validated. 4.2 HTTP Proxies The responder SHOULD set the HTTP headers of the OCSP response in such a way to allow for the intelligent use of HTTP proxy servers. 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. Deacon Expires - May 2004 [Page 7] Lightweight OCSP Profile November 2003 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= - 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 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 this: content-type: application/ocsp-response content-transfer-encoding: binary content-length: date: Fri, 02 May 2003 01:00:00 GMT 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 requestspecifying that proxies should be bypassed by including an appropriate HTTP header in the request (i.e. Pragma: no-cache or Cache-Control: no-cache). 4.3 Caching at Servers Deacon Expires - May 2004 [Page 8] Lightweight OCSP Profile November 2003 In some scenarios it is advantageous to include OCSP response information within the protocol being utilized between the client and server. "Piggybacking" 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 only needs 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. 5. Security Considerations The following considerations apply in addition to the security consideration addressed in Section 5 of [OCSP] 5.1 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 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 Deacon Expires - May 2004 [Page 9] Lightweight OCSP Profile November 2003 responses. If this problem is not repaired, a client with a sufficiently slow clock may also incorrectly accept expired responses for currently revoked certificates. 5.2 Man-in-the-middle attacks To prevent 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 4.2.2.2. 5.3 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. 5.4 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. 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 attacks. 5.5 Modification of HTTP Headers Values included in HTTP headers as described in Section 3 and 4, are not cryptographically protected, they may be manipulated by an attacker. Clients SHOULD use these values for caching guidance Deacon Expires - May 2004 [Page 10] Lightweight OCSP Profile November 2003 only and should ultimately rely on the values present in the signed OCSPResponse. 6. 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. 7. References 7.1 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. 7.2 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, www.openmobilalliance.org. Deacon Expires - May 2004 [Page 11] Lightweight OCSP Profile November 2003 8. 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 Microsoft 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 revocationinformation. 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 ::= {1.3.6.1.4.1.311.21.4} nextPublish EXTENSION ::= { SYNTAX nextPublishSyntax IDENTIFIED BY id-msft-nextPublish } nextPublishSyntax ::= Time Time ::= CHOICE { utcTime UTCTime, generalTime GeneralizedTime } Appendix B. Example OCSP Messages Appendix B.1: OCSP Request SEQUENCE { Deacon Expires - May 2004 [Page 12] Lightweight OCSP Profile November 2003 SEQUENCE { SEQUENCE { SEQUENCE { SEQUENCE { SEQUENCE { OBJECT IDENTIFIER sha1 (1 3 14 3 2 26) NULL } 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 INTEGER 6B 26 79 83 A4 9A B7 C2 3D FF 58 E8 81 AA A5 0E } } } } } Appendix B.2: OCSP Response SEQUENCE { ENUMERATED 0 [0] { SEQUENCE { OBJECT IDENTIFIER ocspBasic (1 3 6 1 5 5 7 48 1 1) OCTET STRING, encapsulates { SEQUENCE { SEQUENCE { [1] { 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 { Deacon Expires - May 2004 [Page 13] Lightweight OCSP Profile November 2003 OBJECT IDENTIFIER organizationalUnitName (2 5 4 11) PrintableString 'Terms of use at https://www.example.com/rpa' '(c)02' } } SET { SEQUENCE { OBJECT IDENTIFIER commonName (2 5 4 3) PrintableString 'Example Class 3 International Server OCSP' 'Responder' } } } } GeneralizedTime 11/09/2003 14:55:57 GMT SEQUENCE { SEQUENCE { SEQUENCE { SEQUENCE { OBJECT IDENTIFIER sha1 (1 3 14 3 2 26) NULL } 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 INTEGER 6B 26 79 83 A4 9A B7 C2 3D FF 58 E8 81 AA A5 0E } [0] Error: Object has zero length. 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 Deacon Expires - May 2004 [Page 14] Lightweight OCSP Profile November 2003 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 } INTEGER 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) NULL } 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 organizationalUnitName (2 5 4 11) PrintableString '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 { Deacon Expires - May 2004 [Page 15] Lightweight OCSP Profile November 2003 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) PrintableString 'Example OCSP Responder' } } } SEQUENCE { SEQUENCE { OBJECT IDENTIFIER rsaEncryption (1 2 840 113549 1 1 1) NULL } BIT STRING, encapsulates { SEQUENCE { INTEGER 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 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 {} Deacon Expires - May 2004 [Page 16] Lightweight OCSP Profile November 2003 } } 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) IA5String 'https://www.example.com/rpa' } } } } } } 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) } } SEQUENCE { OBJECT IDENTIFIER ocspNoCheck (1 3 6 1 5 5 7 48 1 5) OCTET STRING, encapsulates { NULL } } } } } SEQUENCE { Deacon Expires - May 2004 [Page 17] Lightweight OCSP Profile November 2003 OBJECT IDENTIFIER sha1withRSAEncryption (1 2 840 113549 1 1 5) NULL } 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 } } } } } } } } Deacon Expires - May 2004 [Page 18]