CHAPTER 8
698
Interactive Features
KEY
TYPE
VALUE
DigestMethod
array
(Optional;
PDF 1.7)
An array of names indicating acceptable digest algorithms
to use while signing. The valid values are
SHA1
,
SHA256
,
SHA384
,
SHA512
and
RIPEMD160
. The default value is implementation-specific.
Note:
This property is only applicable if the digital credential signing contains
RSA public/private keys. If it contains DSA public/ private key, the digest algo-
rithm is always
SHA1
and this attribute is ignored.
V
real
(Optional)
The minimum required capability of the signature field seed value
dictionary parser. A value of 1 specifies that the parser must be able to recog-
nize all seed value dictionary entries specified in PDF 1.5. A value of 2 specifies
that it must be able to recognize all seed value dictionary entries specified in
PDF 1.7 and earlier.
The
Ff
entry indicates whether this is a required constraint.
Note:
The
PDF Reference fifth edition
(PDF 1.6) and earlier, erroneously indi-
cates that the
V
entry is of type integer. This entry is of type real.
Cert
dictionary
array
(Optional)
A
certificate seed value dictionary
(see Table 8.84) containing infor-
mation about the certificate to be used when signing.
(Optional)
An array of text strings that specifying possible reasons for signing
a document. If specified, the reasons supplied in this entry replace those used
by viewer applications. The
Ff
entry specifies whether one of the reasons in the
array must be used in the signature.
Reasons
•
If the
Reasons
array is provided and the
Ff
entry indicates that
Reasons
is a
required constraint, one of the reasons in the array must be used for the sig-
nature dictionary; otherwise, signing must not take place. If the
Ff
entry in-
dicates
Reasons
is an optional constraint, one of the reasons in the array can
be chosen or a custom reason can be provided.
•
If the
Reasons
array is omitted or contains a single 0-character length string
and the
Ff
entry indicates that
Reasons
is a required constraint, the
Reason
entry must be omitted from the signature dictionary (see Table 8.102).
MDP
dictionary
(Optional; PDF 1.6)
A dictionary containing a single entry whose key is
P
and
whose value is an integer between 0 and 3. A value of 0 defines the signature as
an ordinary (non-author) signature (see Section 8.7, “Digital Signatures”). The
values 1 through 3 are used for author signatures and correspond to the value
of
P
in a
DocMDP
transform parameters dictionary (see Table 8.104).
If this entry is not present or does not contain a
P
entry, no rules are defined
regarding the type of signature or its permissions.