diff options
| -rw-r--r-- | src/add_python/lilliput/ae_common.py | 22 |
1 files changed, 8 insertions, 14 deletions
diff --git a/src/add_python/lilliput/ae_common.py b/src/add_python/lilliput/ae_common.py index f212353..033b5b0 100644 --- a/src/add_python/lilliput/ae_common.py +++ b/src/add_python/lilliput/ae_common.py @@ -35,32 +35,26 @@ def pad10(X): def _tweak_associated_data(t, i, padded): - t_bytes = t//8 - tweak = [0]*(t_bytes) + tweak = list(i.to_bytes(t//8, 'little')) - mask = 0xff - for byte in range(t_bytes-1): - tweak[byte] = (i & mask) >> (byte * 8) - mask = mask << 8 + prefix = 0b0110 if padded else 0b0010 - mask = (0xf << (8 * t_bytes-1)) - tweak[-1] = (i & mask) >> ((t_bytes-1)*8) - if not padded: - tweak[-1] |= 0x20 - else: - tweak[-1] |= 0x60 + # Clear upper 4 bits and set them to prefix. + tweak[-1] &= 0b00001111 + tweak[-1] = prefix << 4 return tweak def build_auth(t, A, key): - Auth = [0 for byte in range(0, BLOCK_BYTES)] + Auth = [0]*BLOCK_BYTES + l_a = len(A)//BLOCK_BYTES need_padding = len(A)%BLOCK_BYTES > 0 A = bytes_to_block_matrix(A) - for i in range(0, l_a): + for i in range(l_a): tweak = _tweak_associated_data(t, i, padded=False) enc = tbc.encrypt(tweak, key, A[i]) Auth = xor(Auth, enc) |