diff options
Diffstat (limited to 'src/ref/lilliput-i.c')
| -rw-r--r-- | src/ref/lilliput-i.c | 26 |
1 files changed, 10 insertions, 16 deletions
diff --git a/src/ref/lilliput-i.c b/src/ref/lilliput-i.c index 97c2117..3ba7ea2 100644 --- a/src/ref/lilliput-i.c +++ b/src/ref/lilliput-i.c @@ -35,32 +35,26 @@ static const uint8_t _0n[BLOCK_BYTES] = { static void _fill_msg_tweak( uint8_t prefix, const uint8_t N[NONCE_BYTES], - uint64_t block_nb, + size_t block_index, uint8_t tweak[TWEAK_BYTES] ) { - /* The 192-bit tweak is filled as follows: + /* With an s-bit block index, the t-bit tweak is filled as follows: * - * - bits 1- 68: block number - * 1- 64: actual 64-bit block number - * 64- 68: 0-padding - * - bits 67-188: nonce - * - bits 189-192: constant 4-bit prefix + * - bits [ 1, t-|N|-4]: block index + * [ 1, s]: actual 64-bit block index + * [ s+1, t-|N|-4]: 0-padding + * - bits [t-|N|-4, t-4]: nonce + * - bits [ t-3, t]: 4-bit prefix */ - for (size_t i=0; i<sizeof(block_nb); i++) - { - uint64_t mask = (uint64_t)0xff << 8*i; - uint8_t b = (mask & block_nb) >> 8*i; - - tweak[i] = b; - } + copy_block_index(block_index, tweak); - tweak[sizeof(block_nb)] = lower_nibble(N[0]) << 4; + tweak[sizeof(block_index)] = lower_nibble(N[0]) << 4; for (size_t i=1; i<NONCE_BYTES; i++) { - tweak[sizeof(block_nb)+i] = lower_nibble(N[i]) << 4 ^ upper_nibble(N[i-1]); + tweak[sizeof(block_index)+i] = lower_nibble(N[i]) << 4 ^ upper_nibble(N[i-1]); } tweak[TWEAK_BYTES-1] = prefix << 4 ^ upper_nibble(N[NONCE_BYTES-1]); |