Adobe 12020596 User Guide - Page 13

Syntax in PDF Reference

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Syntax (Chapter 3 in PDF Reference) This section describes extensions to the PDF specification contained in the PDF Reference, sixth edition, version 1.7 and in ISO 32000 (Document management - Portable document format - PDF 1.7). The latter document is the version of the PDF specification that has been ratified by the ISO. These documents differ as described in About the ISO Draft of the PDF 1.7 Reference. Note: This guide uses italics to identify information not intended for inclusion in the PDF specification. For convenience, the phrase BaseVersion 1.7, Adobe ExtensionLevel 3 is shortened to ExtensionLevel 3 throughout this document. 3.5 Encryption On page 116, modify the paragraph as shown below where unchanged content is shown in gray. The V entry, in specifying which algorithm to use, determines the length of the encryption key, on which the encryption (and decryption) of data in a PDF file is based. For V values 2 and 3, the Length entry specifies the exact length of the encryption key. In PDF 1.5, a value of 4 for V permits the security handler to use its own encryption and decryption algorithms and to specify crypt filters with a key length of 128 bits (16 bytes) to use on specific streams (see Section 3.5.4, "Crypt Filters"). For extension level 3, a value of 5 for V permits the specification of crypt filters with a key length of 256 bits (32 bytes). 13

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13
Syntax (Chapter 3 in PDF Reference)
This section describes extensions to the PDF specification contained in the
PDF Reference, sixth edition,
version 1.7
and in ISO 32000 (
Document management - Portable document format - PDF 1.7
). The latter
document is the version of the PDF specification that has been ratified by the ISO. These documents differ
as described in
About the ISO Draft of the PDF 1.7 Reference
.
Note:
This guide uses italics to identify information not intended for inclusion in the PDF specification. For
convenience, the phrase
BaseVersion 1.7, Adobe ExtensionLevel 3
is shortened to
ExtensionLevel 3
throughout this document.
3.5 Encryption
On page 116, modify the paragraph as shown below where unchanged content is shown in gray.
The
V
entry, in specifying which algorithm to use, determines the length of the encryption key, on which
the encryption (and decryption) of data in a PDF file is based. For
V
values 2 and 3, the
Length
entry
specifies the exact length of the encryption key. In PDF 1.5, a value of 4 for V permits the security handler
to use its own encryption and decryption algorithms and to specify
crypt filters
with a key length of 128
bits (16 bytes)
to use on specific streams (see Section 3.5.4, “Crypt Filters”).
For extension level 3, a value of
5
for
V
permits the specification of crypt filters with a key length of 256 bits (32 bytes).