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Manual: convert more lists to tables

This commit is contained in:
Jay Berkenbilt 2022-01-18 09:03:45 -05:00
parent 3d2d75cfa4
commit 195ddf6f5a
1 changed files with 113 additions and 50 deletions
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manual/encryption.rst
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@ -114,44 +114,69 @@ Algorithm parameters ``V`` and ``R``
encrypting the file, handling keys, etc. It may have any of the
following values:
- 1: The original algorithm, which encrypted files using 40-bit keys.
.. list-table:: Encryption Algorithms: ``V``
:widths: 10 80
:header-rows: 1
- 2: An extension of the original algorithm allowing longer keys.
Introduced in PDF 1.4.
- - V
- Meaning
- 3: An unpublished algorithm that permits file encryption key
lengths ranging from 40 to 128 bits. Introduced in PDF 1.4. qpdf
is believed to be able to read files with ``V`` = 3 but does not
write such files.
- - 1
- The original algorithm, which encrypted files using 40-bit keys.
- 4: An extension of the algorithm that allows it to be
parameterized by additional rules for handling strings and
streams. Introduced in PDF 1.5.
- - 2
- An extension of the original algorithm allowing longer keys.
Introduced in PDF 1.4.
- 5: An algorithm that allows specification of separate security
handlers for strings and streams as well as embedded files, and
which supports 256-bit keys. Introduced in PDF 1.7 extension level
3 and later extended in extension level 8. This is the encryption
system in the PDF 2.0 specification, ISO-32000.
- - 3
- An unpublished algorithm that permits file encryption key
lengths ranging from 40 to 128 bits. Introduced in PDF 1.4.
qpdf is believed to be able to read files with ``V`` = 3 but
does not write such files.
- - 4
- An extension of the algorithm that allows it to be
parameterized by additional rules for handling strings and
streams. Introduced in PDF 1.5.
- - 5
- An algorithm that allows specification of separate security
handlers for strings and streams as well as embedded files,
and which supports 256-bit keys. Introduced in PDF 1.7
extension level 3 and later extended in extension level 8.
This is the encryption system in the PDF 2.0 specification,
ISO-32000.
``R`` is a code specifying the revision of the standard handler. It
is tightly coupled with the value of ``V``. ``R`` may have any of
the following values:
- 2: ``V`` must be 1
.. list-table:: Relationship between ``R`` and ``V``
:widths: 10 80
:header-rows: 1
- 3: ``V`` must be 2 or 3
- - R
- Expected V
- 4: ``V`` must be 4
- - 2
- ``V`` must be 1
- 5: ``V`` must be 5; this extension was never fully specified and
existed for a short time in some versions of Acrobat.
:command:`qpdf` is able to read and write this format, but it
should not be used for any purpose other than testing
compatibility with the format.
- - 3
- ``V`` must be 2 or 3
- 6: ``V`` must be 5. This is the only value that is not deprecated
in the PDF 2.0 specification, ISO-32000.
- - 4
- ``V`` must be 4
- - 5
- ``V`` must be 5; this extension was never fully specified and
existed for a short time in some versions of Acrobat.
:command:`qpdf` is able to read and write this format, but it
should not be used for any purpose other than testing
compatibility with the format.
- - 6
- ``V`` must be 5. This is the only value that is not
deprecated in the PDF 2.0 specification, ISO-32000.
Encryption Dictionary
Encrypted PDF files have an encryption dictionary. There are several
@ -203,12 +228,12 @@ However, the values of bits other than those in the table are ignored,
so having incorrect values probably doesn't break anything in most
cases. A value of 1 indicates that the permission is granted.
.. list-table:: P Parameter
.. list-table:: ``P`` Bit Values
:widths: 10 80
:header-rows: 1
- - bit
- meaning
- - Bit
- Meaning
- - 3
- for ``R`` = 2 printing; for ``R`` >= 3, printing at low
@ -254,45 +279,83 @@ to ``P`` based on the various settings of different security options.
- Start with all bits set except bits 1 and 2, which are cleared
- For ``R`` = 2:
- Clear bits and described in the table below:
- ``--print=n``: clear bit 3
.. list-table:: Command-line Arguments and ``P`` Bit Values
:widths: 20 25 45
:header-rows: 1
- ``--modify=n``: clear bit 4
- - R
- Argument
- Bits Cleared
- ``--extract=n``: clear bit 5
- - R = 2
- ``--print=n``
- 3
- ``--annotate=n``: clear bit 6
- - R = 2
- ``--modify=n``
- 4
- For ``R >= 3``:
- - R = 2
- ``--extract=n``
- 5
- ``--accessibility=n``: for ``R`` = 3, clear bit 10; otherwise,
ignore so bit 10 is always clear if ``R`` >= 4. qpdf allows
creating files with bit 10 clear so that it can be used to create
test files to ensure that a conforming reader ignores the value of
the bit. You should never intentionally clear accessibility.
- - R = 2
- ``--annotate=n``
- 6
- ``--extract=n``: clear bit 5
- - R = 3
- ``--accessibility=n``
- 10
- ``--print=none``: clear bits 3 and 12
- - R >= 4
- ``--accessibility=n``
- ignored
- ``--print=low``: clear bit 12
- - R >= 3
- ``--extract=n``
- 5
- ``--modify=none``: clear bits 4, 6, 9, and 11
- - R >= 3
- ``--print=none``
- 3, 12
- ``--modify=assembly``: clear bits 4, 6, and 9
- - R >= 3
- ``--print=low``
- 12
- ``--modify=form``: clear bits 4 and 6
- - R >= 3
- ``--modify=none``
- 4, 6, 9, 11
- ``--modify=annotate``: clear bit 4
- - R >= 3
- ``--modify=assembly``
- 4, 6, 9
- ``--assemble=n``: clear bit 11
- - R >= 3
- ``--modify=form``
- 4, 6
- ``--annotate=n``: clear bit 6
- - R >= 3
- ``--modify=annotate``
- 4
- ``--form=n``: clear bit 9
- - R >= 3
- ``--assemble=n``
- 11
- ``--modify-other=n``: clear bit 4
- - R >= 3
- ``--annotate=n``
- 6
- - R >= 3
- ``--form=n``
- 9
- - R >= 3
- ``--modify-other=n``
- 4
Options to :command:`qpdf`, both at the CLI and library level, allow
more granular clearing of permission bits than do most tools,