diff options
Diffstat (limited to 'src/ref/lilliput-ii.c')
| -rw-r--r-- | src/ref/lilliput-ii.c | 14 |
1 files changed, 13 insertions, 1 deletions
diff --git a/src/ref/lilliput-ii.c b/src/ref/lilliput-ii.c index 8238b08..7c02bce 100644 --- a/src/ref/lilliput-ii.c +++ b/src/ref/lilliput-ii.c @@ -32,6 +32,8 @@ static void _init_msg_tweak(const uint8_t tag[TAG_BYTES], uint8_t tweak[TWEAK_BY * [ 1, 64]: tag[ 1.. 64] XOR block index * [ 65, t-1]: tag[65..t-1] * - bit t: 1 + * + * This function sets bits 65 to t once and for all. */ memcpy(tweak+sizeof(uint64_t), tag+sizeof(uint64_t), TAG_BYTES-sizeof(uint64_t)); @@ -40,7 +42,17 @@ static void _init_msg_tweak(const uint8_t tag[TAG_BYTES], uint8_t tweak[TWEAK_BY static void _fill_msg_tweak(const uint8_t tag[TAG_BYTES], uint64_t block_index, uint8_t tweak[TWEAK_BYTES]) { - /* Assume bits 65 to t-1 are set. */ + /* The t-bit tweak is filled as follows: + * + * - bits [ 1, t-1]: tag + block index + * [ 1, 64]: tag[ 1.. 64] XOR block index + * [ 65, t-1]: tag[65..t-1] + * - bit t: 1 + * + * This function assumes bits 65 to t have already been set, and + * only sets bits 1 to 64. + */ + for (size_t i=0; i<sizeof(block_index); i++) { uint8_t index_i = block_index >> i*8 & 0xff; |