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aes: Implement AES-128-CBC decryption function 

Implement a compatible AES-128-CBC decryption function as a counterpart
of the encryption function pulled from tegra20-common/crypto.c .

Signed-off-by: Marek Vasut <marex@denx.de>
This commit is contained in:
Marek Vasut 2014-03-05 19:58:38 +01:00 committed by Tom Rini
parent 6e7b9f4fa0
commit dc24bb6ddb
2 changed files with 38 additions and 0 deletions
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10
include/aes.h
View File

@ -63,4 +63,14 @@ void aes_decrypt(u8 *in, u8 *expkey, u8 *out);
*/
void aes_cbc_encrypt_blocks(u8 *key_exp, u8 *src, u8 *dst, u32 num_aes_blocks);
/**
* Decrypt multiple blocks of data with AES CBC.
*
* @key_exp Expanded key to use
* @src Source data to decrypt
* @dst Destination buffer
* @num_aes_blocks Number of AES blocks to decrypt
*/
void aes_cbc_decrypt_blocks(u8 *key_exp, u8 *src, u8 *dst, u32 num_aes_blocks);
#endif /* _AES_REF_H_ */

28
lib/aes.c
View File

@ -632,3 +632,31 @@ void aes_cbc_encrypt_blocks(u8 *key_exp, u8 *src, u8 *dst, u32 num_aes_blocks)
dst += AES_KEY_LENGTH;
}
}
void aes_cbc_decrypt_blocks(u8 *key_exp, u8 *src, u8 *dst, u32 num_aes_blocks)
{
u8 tmp_data[AES_KEY_LENGTH], tmp_block[AES_KEY_LENGTH];
/* Convenient array of 0's for IV */
u8 cbc_chain_data[AES_KEY_LENGTH] = { 0 };
u32 i;
for (i = 0; i < num_aes_blocks; i++) {
debug("encrypt_object: block %d of %d\n", i, num_aes_blocks);
debug_print_vector("AES Src", AES_KEY_LENGTH, src);
memcpy(tmp_block, src, AES_KEY_LENGTH);
/* Decrypt the AES block */
aes_decrypt(src, key_exp, tmp_data);
debug_print_vector("AES Xor", AES_KEY_LENGTH, tmp_data);
/* Apply the chain data */
apply_cbc_chain_data(cbc_chain_data, tmp_data, dst);
debug_print_vector("AES Dst", AES_KEY_LENGTH, dst);
/* Update pointers for next loop. */
memcpy(cbc_chain_data, tmp_block, AES_KEY_LENGTH);
src += AES_KEY_LENGTH;
dst += AES_KEY_LENGTH;
}
}