I think the siv code could benefit from a funtion to create a cmac digest in one step, without the update/digest split and the intermediate buffer. That would be something like
cmac128_message(const struct cmac128_key *key, const void *cipher, nettle_crypt_func *encrypt, size_t digest_length, uint8_t *digest, size_t message_length, const uint8_t *message);
Then the key need to be taken out from the cmac128_ctx. I'm trying that out, on the branch cmac-layout. Patch below. What do you think?
Regards, /Niels
commit 9b41e3b82b567abb68c1b7fc3b1e6b1a4ed87b26 Author: Niels Möller nisse@lysator.liu.se Date: 2019-06-01 10:30:29 +0200
New struct cmac128_key.
diff --git a/ChangeLog b/ChangeLog index 53cdc41d..a7a4355f 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,9 @@ +2019-06-01 Niels Möller nisse@lysator.liu.se + + * cmac.h (struct cmac128_key): New struct. + * cmac.h (struct cmac128_ctx): Use struct cmac128_key. + * cmac.c (cmac128_set_key, cmac128_digest): Update accordingly. + 2019-05-12 Niels Möller nisse@lysator.liu.se
Delete old libdes/openssl compatibility interface. diff --git a/cmac.c b/cmac.c index ed3b5eb8..07d805f3 100644 --- a/cmac.c +++ b/cmac.c @@ -83,8 +83,8 @@ cmac128_set_key(struct cmac128_ctx *ctx, const void *cipher, /* step 1 - generate subkeys k1 and k2 */ encrypt(cipher, 16, L->b, const_zero);
- block_mulx(&ctx->K1, L); - block_mulx(&ctx->K2, &ctx->K1); + block_mulx(&ctx->key.K1, L); + block_mulx(&ctx->key.K2, &ctx->key.K1); }
#define MIN(x,y) ((x)<(y)?(x):(y)) @@ -148,11 +148,11 @@ cmac128_digest(struct cmac128_ctx *ctx, const void *cipher, if (ctx->index < 16) { ctx->block.b[ctx->index] = 0x80; - memxor(ctx->block.b, ctx->K2.b, 16); + memxor(ctx->block.b, ctx->key.K2.b, 16); } else { - memxor(ctx->block.b, ctx->K1.b, 16); + memxor(ctx->block.b, ctx->key.K1.b, 16); }
memxor3(Y.b, ctx->block.b, ctx->X.b, 16); diff --git a/cmac.h b/cmac.h index 6d107982..9d972ea5 100644 --- a/cmac.h +++ b/cmac.h @@ -55,18 +55,22 @@ extern "C" { #define cmac_aes256_update nettle_cmac_aes256_update #define cmac_aes256_digest nettle_cmac_aes256_digest
-struct cmac128_ctx +struct cmac128_key { - /* Key */ union nettle_block16 K1; union nettle_block16 K2; +}; + +struct cmac128_ctx +{ + struct cmac128_key key;
/* MAC state */ union nettle_block16 X;
/* Block buffer */ - union nettle_block16 block; size_t index; + union nettle_block16 block; };
void