CHAPTER 3
122
Syntax
If revision 4 is specified, the standard security handler supports crypt filters (see
Identity
crypt filter
(see Table 3.23) and crypt filters named
StdCF
whose dictionaries contain a
CFM
value of
V2
or
AESV2
and an
AuthEvent
value of
DocOpen
.
Note:
Once the document has been opened and decrypted successfully, the applica-
tion has access to the entire contents of the document. There is nothing inherent in
PDF encryption that enforces the document permissions specified in the encryption
dictionary. It is up to the implementors of PDF consumer applications to respect the
intent of the document creator by restricting user access to an encrypted PDF file ac-
cording to the permissions contained in the file.
Note:
PDF 1.5 introduces a set of access permissions that do not require the docu-
ment to be encrypted; see Section 8.7.3, “Permissions.”
Standard Encryption Dictionary
handler (in addition to those in Table 3.18).
TABLE 3.19 Additional encryption dictionary entries for the standard security handler
KEY
TYPE
VALUE
R
number
(Required)
A number specifying which revision of the standard security handler
should be used to interpret this dictionary:
•
2 if the document is encrypted with a
V
value less than 2 (see Table 3.18) and
does not have any of the access permissions set (by means of the
P
entry, below)
that are designated “Revision 3 or greater” in Table 3.20
•
3 if the document is encrypted with a
V
value of 2 or 3, or has any “Revision 3
or greater” access permissions set
•
4 if the document is encrypted with a
V
value of 4
O
string
(Required)
A 32-byte string, based on both the owner and user passwords, that is
used in computing the encryption key and in determining whether a valid owner
password was entered. For more information, see “Encryption Key Algorithm” on