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                                                         740
           CHAPTER 8                                                                 Interactive Features



           Adobe's      Revocation       Information       attribute     value     has    ASN.1       type
           RevocationInfoArchival:
               RevocationInfoArchival ::= SEQUENCE {
                  crl          [0] EXPLICIT SEQUENCE of CRLs, OPTIONAL
                  ocsp         [1] EXPLICIT SEQUENCE of OCSP Responses, OPTIONAL
                  otherRevInfo [2] EXPLICIT SEQUENCE of OtherRevInfo, OPTIONAL
               }
               OtherRevInfo ::= SEQUENCE {
               Type OBJECT IDENTIFIER
               Value OCTET STRING
               }

           For byte range signatures, Contents is a hexadecimal string with “<” and “>” de-
           limiters. It must fit precisely in the space between the ranges specified by
           ByteRange. Since the length of PKCS#7 objects is not entirely predictable, it is of-
           ten necessary to pad the value of Contents with zeros at the end of the string (be-
           fore the “>” delimiter) before writing the PKCS#7 to the allocated space in the file.

           The most common format for encoding signature values is adbe.pkcs7.detached.
           This encoding allows the most options in terms of algorithm use. The following
           table shows the algorithms supported for the various SubFilter values.

                                                                 SubFilter value
                             adbe.pkcs7.detached            adbe.pkcs7.sha1                adbe.x509.rsa.sha1a

Message Digest               SHA1 (PDF 1.3)                 SHA1 (PDF 1.3)b                SHA1 (PDF 1.3)
                             SHA256 (PDF 1.6)                                              SHA256 (PDF 1.6)
                             SHA384 (PDF 1.7)                                              SHA384 (PDF 1.7)
                             SHA512 (PDF 1.7)                                              SHA512 (PDF 1.7)
                             RIPEMD160 (PDF 1.7)                                           RIPEMD160 (PDF 1.7)

RSA Algorithm Support        Up to 1024-bit (PDF 1.3)       See adbe.pkcs7.detached        See
                             Up to 2048-bit (PDF 1.5)                                      adbe.pkcs7.detached
                             Up to 4096-bit (PDF 1.5)

DSA Algorithm Support        Up to 4096-bits (PDF 1.6)      See adbe.pkcs7.detached        No

a. Despite the appearance of sha1 in the name of this SubFilter value, supported encodings are not limited to the
   SHA1 algorithm. The PKCS#1 object contains an identifier that indicates which algorithm is used.
b. Other digest algorithms may be used to digest the signed-data field; however, SHA1 is always used to digest the
   data that is being signed.

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