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                                                       729
             SECTION 8.7                                                            Digital Signatures



KEY                 TYPE           VALUE

V                   integer        (Optional; PDF 1.5) The version of the signature dictionary format. It corre-
                                   sponds to the usage of the signature dictionary in the context of the value of
                                   SubFilter. The value is 1 if the Reference dictionary is considered critical to
                                   the validation of the signature.
                                   Default value: 0.

Prop_Build          dictionary     (Optional; PDF 1.5) A dictionary that can be used by a signature handler to
                                   record information that captures the state of the computer environment used
                                   for signing, such as the name of the handler used to create the signature, soft-
                                   ware build date, version, and operating system.
                                   Adobe publishes a separate specification, the PDF Signature Build Dictionary
                                   Specification for Acrobat 6.0 that provides implementation guidelines for the
                                   use of this dictionary.

Prop_AuthTime       integer        (Optional; PDF 1.5) The number of seconds since the signer was last authen-
                                   ticated. It is intended to be used in claims of signature repudiation. It should
                                   be omitted if the value is unknown.

Prop_AuthType       name           (Optional; PDF 1.5) The method used to authenticate the signer. It is intend-
                                   ed to be used in claims of signature repudiation. Valid values include PIN,
                                   Password, and Fingerprint.

             Note: The entries in the signature dictionary can be conceptualized as being in dif-
             ferent dictionaries; they are in one dictionary for historical and cryptographic rea-
             sons. The categories are signature properties (R, M, Name, Reason, Location,
             Prop_Build, Prop_AuthTime, and Prop_AuthType); key information (Cert and por-
             tions of Contents when the signature value is a PKCS#7 object); reference
             (Reference and ByteRange); and signature value (Contents when the signature val-
             ue is a PKCS#1 object).

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