CHAPTER 3
90
Syntax
3.3.9 Crypt Filter
The
Crypt
filter
(PDF 1.5)
allows the document-level security handler (see
decrypt the input data. The
Name
parameter in the decode parameters dictionary
for this filter (see Table 3.12) specifies which of the named crypt filters in the
document (see Section 3.5.4, “Crypt Filters”) should be used.
TABLE 3.12 Optional parameters for Crypt filters
KEY
TYPE
VALUE
Type
name
name
(Optional)
If present, must be
CryptFilterDecodeParms
for a
Crypt
filter de-
code parameter dictionary.
(Optional)
The name of the crypt filter that is to be used to decrypt this
stream. The name must correspond to an entry in the
CF
entry of the encryp-
tion dictionary (see Table 3.18) or one of the standard crypt filters (see
Default value:
Identity
.
Name
In addition, the decode parameters dictionary may include entries that are
private to the security handler. Security handlers may use information from both
the crypt filter decode parameters dictionary and the crypt filter dictionaries (see
Note:
When adding private data to the decode parameters dictionary, security han-
dlers should name these entries in conformance with the PDF name registry (see
3.4 File Structure
The preceding sections describe the syntax of individual objects. This section
describes how objects are organized in a PDF file for efficient random access and
incremental update. A canonical PDF file initially consists of four elements (see
•
A one-line
header
identifying the version of the PDF specification to which the
file conforms
•
A
body
containing the objects that make up the document contained in the file