[implem-python] Création d'un paquet "lilliput"

1 files changed, 155 insertions, 0 deletions

diff --git a/python/lilliput/lilliput_ae_1.py b/python/lilliput/lilliput_ae_1.py
new file mode 100644
index 0000000..0da2a95
--- /dev/null
+++ b/python/lilliput/lilliput_ae_1.py
@@ -0,0 +1,155 @@
+"""
+    OCB 3 for lilliput ae i
+"""
+
+from enum import Enum
+
+from .constants import BLOCK_BYTES, NONCE_BYTES
+from .helpers import (
+    ArrayToBlockbytesMatrix,
+    BlockbytesMatrixToBytes,
+    BuildAuth,
+    Padding10LSB,
+    TagValidationError,
+    XorState
+)
+from . import tbc
+
+
+TWEAK_BITS = 192
+TWEAK_BYTES = TWEAK_BITS//8
+
+
+def LowPart(array, number_bits):
+    shifted = 0
+    for byte in range(0, len(array)):
+        shifted |= (array[byte] << (8 * byte))
+
+    mask = 0
+    for bit in range(0, number_bits):
+        mask |= (0x1 << bit)
+
+    lower_part = shifted & mask
+
+    will_pad = 0
+    if number_bits % 8 != 0:
+        will_pad = 1
+
+    lower_part_byte = []
+    nb_bytes = number_bits//8 + will_pad
+    for byte in range(nb_bytes):
+        lower_part_byte.append(lower_part & 0xff)
+        lower_part = lower_part >> 8
+
+    return lower_part_byte
+
+
+class _MessageTweak(Enum):
+    BLOCK = 0b000
+    NO_PADDING = 0b0001
+    PAD = 0b0100
+    FINAL = 0b0101
+
+
+def TweakMessage(N, j, padding):
+    tweak = [0 for byte in range(0, TWEAK_BYTES)]
+    for byte in range(NONCE_BYTES-1, -1, -1):
+        tweak[byte + (TWEAK_BYTES-NONCE_BYTES)] |= (N[byte] & 0xf0) >> 4
+        tweak[byte + (TWEAK_BYTES-NONCE_BYTES-1)] |= (N[byte] & 0x0f) << 4
+
+    tweak[TWEAK_BYTES-NONCE_BYTES-1] |= ((j >> 64) & 0xf)
+    for byte in range(TWEAK_BYTES-NONCE_BYTES-2, -1, -1):
+        tweak[byte] = (j >> (8 * byte)) & 0xff
+
+    tweak[-1] |= padding.value<<4
+
+    return tweak
+
+
+def TreatMessageEnc(M, N, key):
+    checksum = [0 for byte in range(0, BLOCK_BYTES)]
+
+    l = len(M)//BLOCK_BYTES
+    padding_bytes = len(M)%BLOCK_BYTES
+
+    M = ArrayToBlockbytesMatrix(M)
+    C = []
+
+    for j in range(0, l):
+        checksum = XorState(checksum, M[j])
+        tweak = TweakMessage(N, j, _MessageTweak.BLOCK)
+        C.append(tbc.encrypt(tweak, key, M[j]))
+
+    if padding_bytes == 0:
+        tweak = TweakMessage(N, l, _MessageTweak.NO_PADDING)
+        Final = tbc.encrypt(tweak, key, checksum)
+
+    else:
+        m_padded = Padding10LSB(M[l])
+        checksum = XorState(checksum, m_padded)
+        tweak = TweakMessage(N, l, _MessageTweak.PAD)
+        pad = tbc.encrypt(tweak, key, [0 for byte in range(0, BLOCK_BYTES)])
+
+        lower_part = LowPart(pad, padding_bytes*8)
+        C.append(XorState(M[l], lower_part))
+        tweak_final = TweakMessage(N, l+1, _MessageTweak.FINAL)
+        Final = tbc.encrypt(tweak_final, key, checksum)
+
+    return (Final, C)
+
+
+def TreatMessageDec(C, N, key):
+    checksum = [0 for byte in range(0, BLOCK_BYTES)]
+
+    l = len(C)//BLOCK_BYTES
+    padding_bytes = len(C)%BLOCK_BYTES
+
+    C = ArrayToBlockbytesMatrix(C)
+    M = []
+
+    for j in range(0, l):
+        tweak = TweakMessage(N, j, _MessageTweak.BLOCK)
+        M.append(tbc.decrypt(tweak, key, C[j]))
+        checksum = XorState(checksum, M[j])
+
+    if padding_bytes == 0:
+        tweak = TweakMessage(N, l, _MessageTweak.NO_PADDING)
+        Final = tbc.encrypt(tweak, key, checksum)
+
+    else:
+        tweak = TweakMessage(N, l, _MessageTweak.PAD)
+        pad = tbc.encrypt(tweak, key, [0 for byte in range(0, BLOCK_BYTES)])
+        lower_part = LowPart(pad, padding_bytes*8)
+        M.append(XorState(C[l], lower_part))
+
+        m_padded = Padding10LSB(M[l])
+        checksum = XorState(checksum, m_padded)
+        tweak_final = TweakMessage(N, l+1, _MessageTweak.FINAL)
+        Final = tbc.encrypt(tweak_final, key, checksum)
+
+    return (Final, M)
+
+
+################################################################################
+def encrypt(A, M, N, key):
+    K = list(key)
+
+    Auth = BuildAuth(TWEAK_BITS, A, K)
+    (Final, C) = TreatMessageEnc(M, N, K)
+    tag = XorState(Auth, Final)
+
+    return BlockbytesMatrixToBytes(C), bytes(tag)
+
+
+def decrypt(A, C, N, tag, key):
+    K = list(key)
+    tag = list(tag)
+
+    Auth = BuildAuth(TWEAK_BITS, A, K)
+    (Final, M) = TreatMessageDec(C, N, K)
+    tag2 = XorState(Auth, Final)
+
+    if tag != tag2:
+        raise TagValidationError(tag, tag2)
+
+    return BlockbytesMatrixToBytes(M)