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dm crypt: add multi key capability

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This patch adds generic multikey handling to be used
in following patch for Loop-AES mode compatibility.

This patch extends mapping table to optional keycount and
implements generic multi-key capability.

With more keys defined the <key> string is divided into
several <keycount> sections and these are used for tfms.

The tfm is used according to sector offset
(sector 0->tfm[0], sector 1->tfm[1], sector N->tfm[N modulo keycount])
(only power of two values supported for keycount here).

Because of tfms per-cpu allocation, this mode can be take
a lot of memory on large smp systems.

Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Cc: Max Vozeler <max@hinterhof.net>
This commit is contained in:
Milan Broz
2011-01-13 19:59:54 +00:00
committed by Alasdair G Kergon
parent 2dc5327d3a
commit d1f9642381
2 changed files with 70 additions and 22 deletions
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7
Documentation/device-mapper/dm-crypt.txt
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@@ -8,7 +8,7 @@ Parameters: <cipher> <key> <iv_offset> <device path> <offset>
<cipher>
Encryption cipher and an optional IV generation mode.
(In format cipher-chainmode-ivopts:ivmode).
(In format cipher[:keycount]-chainmode-ivopts:ivmode).
Examples:
des
aes-cbc-essiv:sha256
@@ -20,6 +20,11 @@ Parameters: <cipher> <key> <iv_offset> <device path> <offset>
Key used for encryption. It is encoded as a hexadecimal number.
You can only use key sizes that are valid for the selected cipher.
<keycount>
Multi-key compatibility mode. You can define <keycount> keys and
then sectors are encrypted according to their offsets (sector 0 uses key0;
sector 1 uses key1 etc.). <keycount> must be a power of two.
<iv_offset>
The IV offset is a sector count that is added to the sector number
before creating the IV.