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authorMilan Broz <mbroz@redhat.com>2011-01-13 19:59:54 +0000
committerAlasdair G Kergon <agk@redhat.com>2011-01-13 19:59:54 +0000
commitd1f9642381847e2b94caa34c3533211cf36ffcf4 (patch)
tree32ae1cc4b0946247384fe1a31e257658f734b3f7 /Documentation/device-mapper
parent2dc5327d3acb3340ab6fa3981401b076b78a51f4 (diff)
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dm crypt: add multi key capability
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>
Diffstat (limited to 'Documentation/device-mapper')
-rw-r--r--Documentation/device-mapper/dm-crypt.txt7
1 files changed, 6 insertions, 1 deletions
diff --git a/Documentation/device-mapper/dm-crypt.txt b/Documentation/device-mapper/dm-crypt.txt
index 524de926290d..59293ac4a5d0 100644
--- a/Documentation/device-mapper/dm-crypt.txt
+++ b/Documentation/device-mapper/dm-crypt.txt
@@ -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.