int skein_ctx_prepare(struct skein_ctx *ctx, enum skein_size size)
{
skein_assert_ret(ctx && size, SKEIN_FAIL);
memset(ctx, 0, sizeof(struct skein_ctx));
ctx->skein_size = size;
return SKEIN_SUCCESS;
}
int skein_mac_init(struct skein_ctx *ctx, const u8 *key, size_t key_len,
size_t hash_bit_len)
{
int ret = SKEIN_FAIL;
u64 *x = NULL;
size_t x_len = 0;
u64 tree_info = SKEIN_CFG_TREE_INFO_SEQUENTIAL;
skein_assert_ret(ctx, SKEIN_FAIL);
x = ctx->m.s256.x;
x_len = ctx->skein_size/8;
skein_assert_ret(hash_bit_len, SKEIN_BAD_HASHLEN);
switch (ctx->skein_size) {
case SKEIN_256:
ret = skein_256_init_ext(&ctx->m.s256, hash_bit_len,
tree_info,
(const u8 *)key, key_len);
break;
case SKEIN_512:
ret = skein_512_init_ext(&ctx->m.s512, hash_bit_len,
tree_info,
(const u8 *)key, key_len);
break;
case SKEIN_1024:
ret = skein_1024_init_ext(&ctx->m.s1024, hash_bit_len,
tree_info,
(const u8 *)key, key_len);
break;
}
if (ret == SKEIN_SUCCESS) {
/*
* Save chaining variables for this combination of key,
* key_len, hash_bit_len
*/
memcpy(ctx->x_save, x, x_len);
}
return ret;
}
int skein_update_bits(struct skein_ctx *ctx, const u8 *msg,
size_t msg_bit_cnt)
{
/*
* I've used the bit pad implementation from skein_test.c (see NIST CD)
* and modified it to use the convenience functions and added some
* pointer arithmetic.
*/
size_t length;
u8 mask;
u8 *up;
/*
* only the final Update() call is allowed do partial bytes, else
* assert an error
*/
skein_assert_ret((ctx->m.h.T[1] & SKEIN_T1_FLAG_BIT_PAD) == 0 ||
msg_bit_cnt == 0, SKEIN_FAIL);
/* if number of bits is a multiple of bytes - that's easy */
if ((msg_bit_cnt & 0x7) == 0)
return skein_update(ctx, msg, msg_bit_cnt >> 3);
skein_update(ctx, msg, (msg_bit_cnt >> 3) + 1);
/*
* The next line rely on the fact that the real Skein contexts
* are a union in our context. After the addition the pointer points to
* Skein's real partial block buffer.
* If this layout ever changes we have to adapt this as well.
*/
up = (u8 *)ctx->m.s256.x + ctx->skein_size / 8;
/* set tweak flag for the skein_final call */
skein_set_bit_pad_flag(ctx->m.h);
/* now "pad" the final partial byte the way NIST likes */
/* get the b_cnt value (same location for all block sizes) */
length = ctx->m.h.b_cnt;
/* internal sanity check: there IS a partial byte in the buffer! */
skein_assert(length != 0);
/* partial byte bit mask */
mask = (u8)(1u << (7 - (msg_bit_cnt & 7)));
/* apply bit padding on final byte (in the buffer) */
up[length - 1] = (up[length - 1] & (0 - mask)) | mask;
return SKEIN_SUCCESS;
}
int skein_init(struct skein_ctx *ctx, size_t hash_bit_len)
{
int ret = SKEIN_FAIL;
size_t x_len = 0;
u64 *x = NULL;
u64 tree_info = SKEIN_CFG_TREE_INFO_SEQUENTIAL;
skein_assert_ret(ctx, SKEIN_FAIL);
/*
* The following two lines rely of the fact that the real Skein
* contexts are a union in out context and thus have tha maximum
* memory available. The beauty of C :-) .
*/
x = ctx->m.s256.x;
x_len = ctx->skein_size / 8;
/*
* If size is the same and hash bit length is zero then reuse
* the save chaining variables.
*/
switch (ctx->skein_size) {
case SKEIN_256:
ret = skein_256_init_ext(&ctx->m.s256, hash_bit_len,
tree_info, NULL, 0);
break;
case SKEIN_512:
ret = skein_512_init_ext(&ctx->m.s512, hash_bit_len,
tree_info, NULL, 0);
break;
case SKEIN_1024:
ret = skein_1024_init_ext(&ctx->m.s1024, hash_bit_len,
tree_info, NULL, 0);
break;
}
if (ret == SKEIN_SUCCESS) {
/*
* Save chaining variables for this combination of size and
* hash_bit_len
*/
memcpy(ctx->x_save, x, x_len);
}
return ret;
}
int skein_final(struct skein_ctx *ctx, u8 *hash)
{
int ret = SKEIN_FAIL;
skein_assert_ret(ctx, SKEIN_FAIL);
switch (ctx->skein_size) {
case SKEIN_256:
ret = skein_256_final(&ctx->m.s256, hash);
break;
case SKEIN_512:
ret = skein_512_final(&ctx->m.s512, hash);
break;
case SKEIN_1024:
ret = skein_1024_final(&ctx->m.s1024, hash);
break;
}
return ret;
}
int skein_update(struct skein_ctx *ctx, const u8 *msg,
size_t msg_byte_cnt)
{
int ret = SKEIN_FAIL;
skein_assert_ret(ctx, SKEIN_FAIL);
switch (ctx->skein_size) {
case SKEIN_256:
ret = skein_256_update(&ctx->m.s256, msg, msg_byte_cnt);
break;
case SKEIN_512:
ret = skein_512_update(&ctx->m.s512, msg, msg_byte_cnt);
break;
case SKEIN_1024:
ret = skein_1024_update(&ctx->m.s1024, msg, msg_byte_cnt);
break;
}
return ret;
}