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authorJoy Latten <latten@austin.ibm.com>2007-10-23 08:50:32 +0800
committerHerbert Xu <herbert@gondor.apana.org.au>2008-01-11 08:16:01 +1100
commit23e353c8a681cc30d42fbd4f2c2be85c44fe209b (patch)
treed64934fa42e3e1e2b3fcccb4e86168a1614e250d /drivers/crypto/Makefile
parent490fe3f05be3f7c87d7932bcb6e6e53e3db2cd9c (diff)
downloadlinux-linaro-stable-23e353c8a681cc30d42fbd4f2c2be85c44fe209b.tar.gz
[CRYPTO] ctr: Add CTR (Counter) block cipher mode
This patch implements CTR mode for IPsec. It is based off of RFC 3686. Please note: 1. CTR turns a block cipher into a stream cipher. Encryption is done in blocks, however the last block may be a partial block. A "counter block" is encrypted, creating a keystream that is xor'ed with the plaintext. The counter portion of the counter block is incremented after each block of plaintext is encrypted. Decryption is performed in same manner. 2. The CTR counterblock is composed of, nonce + IV + counter The size of the counterblock is equivalent to the blocksize of the cipher. sizeof(nonce) + sizeof(IV) + sizeof(counter) = blocksize The CTR template requires the name of the cipher algorithm, the sizeof the nonce, and the sizeof the iv. ctr(cipher,sizeof_nonce,sizeof_iv) So for example, ctr(aes,4,8) specifies the counterblock will be composed of 4 bytes from a nonce, 8 bytes from the iv, and 4 bytes for counter since aes has a blocksize of 16 bytes. 3. The counter portion of the counter block is stored in big endian for conformance to rfc 3686. Signed-off-by: Joy Latten <latten@austin.ibm.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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