[implem-python] Extraction de fonctions communes aux deux modes

2 files changed, 77 insertions, 64 deletions

diff --git a/python/helpers.py b/python/helpers.py
index 34949a4..3d741b0 100644
--- a/python/helpers.py
+++ b/python/helpers.py
@@ -1,4 +1,5 @@
-from constants import BLOCK_BYTES
+from constants import BLOCK_BITS, BLOCK_BYTES
+from lilliput_tbc import LilliputTBCEnc
 
 
 def ArrayToBlockbytesMatrix(array) :
@@ -23,3 +24,66 @@ def ArrayToBlockbytesMatrix(array) :
 def BlockbytesMatrixToBytes(matrix):
     return bytes(byte for block in matrix for byte in block)
 
+
+def XorState(state1, state2):
+    return list(
+        s1^s2 for (s1, s2) in zip(state1, state2)
+    )
+
+
+def Padding10LSB(array, number_bits):
+    shifted = 0
+    for byte in range(0, len(array)):
+        shifted |= (array[byte] << (8 * byte))
+    shifted = (shifted << (BLOCK_BITS - number_bits)) & 0xffffffffffffffffffffffffffffffff
+
+    padded = shifted | (0x1 << (BLOCK_BITS - number_bits - 1))
+
+    array_padded = [0 for byte in range(0, BLOCK_BYTES)]
+    for byte in range(0, BLOCK_BYTES):
+        array_padded[byte] = (padded & (0xff << (8 * byte))) >> (8 * byte)
+
+    return array_padded
+
+
+def _tweakAssociatedData(t, i, padded):
+    t_bytes = t//8
+    tweak = [0]*(t_bytes)
+
+    mask = 0xff
+    for byte in range(t_bytes-1):
+        tweak[byte] = (i & mask) >> (byte * 8)
+        mask = mask << 8
+
+    mask = (0xf << (8 * t_bytes-1))
+    tweak[-1] = (i & mask) >> ((t_bytes-1)*8)
+    if not padded:
+        tweak[-1] |= 0x20
+    else:
+        tweak[-1] |= 0x60
+
+    return tweak
+
+
+def BuildAuth(t, A, key):
+    Auth = [0 for byte in range(0, BLOCK_BYTES)]
+    l_a = len(A)//BLOCK_BYTES
+
+    padding_bytes = len(A)%BLOCK_BYTES
+
+    A = ArrayToBlockbytesMatrix(A)
+
+    for i in range(0, l_a):
+        tweak = _tweakAssociatedData(t, i, padded=False)
+        enc = LilliputTBCEnc(tweak, key, A[i])
+        Auth = XorState(Auth, enc)
+
+    if padding_bytes == 0:
+        return Auth
+
+    tweak = _tweakAssociatedData(t, l_a, padded=True)
+    ad_padded = Padding10LSB(A[l_a], padding_bytes*8)
+    enc = LilliputTBCEnc(tweak, key, ad_padded)
+    Auth = XorState(Auth, enc)
+
+    return Auth
diff --git a/python/lilliput_ae_1.py b/python/lilliput_ae_1.py
index c9a731e..8cf55bb 100644
--- a/python/lilliput_ae_1.py
+++ b/python/lilliput_ae_1.py
@@ -2,10 +2,17 @@
     OCB 3 for lilliput ae i
 """
 
-import lilliput_tbc as ltbc
-from constants import BLOCK_BITS, BLOCK_BYTES, NONCE_BYTES
 from enum import Enum
-from helpers import ArrayToBlockbytesMatrix, BlockbytesMatrixToBytes
+
+import lilliput_tbc as ltbc
+from constants import BLOCK_BYTES, NONCE_BYTES
+from helpers import (
+    ArrayToBlockbytesMatrix,
+    BlockbytesMatrixToBytes,
+    BuildAuth,
+    Padding10LSB,
+    XorState
+)
 
 
 KEY_BITS = 128
@@ -35,26 +42,6 @@ def InitParameters(key_bits) :
 
 ###############################################################################
 
-def XorState(state1, state2) :
-    state_output = [state1[byte] ^ state2[byte] for byte in range(0, len(state1))]
-    return state_output
-
-
-def Padding10LSB(array, number_bits) :
-    shifted = 0
-    for byte in range(0, len(array)) :
-        shifted |= (array[byte] << (8 * byte))
-    shifted = (shifted << (BLOCK_BITS - number_bits)) & 0xffffffffffffffffffffffffffffffff
-
-    padded = shifted | (0x1 << (BLOCK_BITS - number_bits - 1))
-
-    array_padded = [0 for byte in range(0, BLOCK_BYTES)]
-    for byte in range(0, BLOCK_BYTES) :
-        array_padded[byte] = (padded & (0xff << (8 * byte))) >> (8 * byte)
-
-    return array_padded
-
-
 def LowPart(array, number_bits) :
     shifted = 0
     for byte in range(0, len(array)) :
@@ -79,45 +66,7 @@ def LowPart(array, number_bits) :
 
 ###############################################################################
 
-def TweakAssociatedData(i, padded) :
-    tweak = [0 for byte in range(0, TWEAK_BYTES)]
-
-    mask = 0xff
-    for byte in range(0, TWEAK_BYTES - 1) :
-        tweak[byte] = (i & mask) >> (byte * 8)
-        mask = mask << 8
-
-    mask = (0xf << (8 * (TWEAK_BYTES - 1)))
-    tweak[TWEAK_BYTES - 1] = (i & mask) >> ((TWEAK_BYTES - 1) * 8)
-    if not padded:
-        tweak[TWEAK_BYTES - 1] |= 0x20
-    else :
-        tweak[TWEAK_BYTES - 1] |= 0x60
-    return tweak
-
-
-def BuildAuth(A, key) :
-    Auth = [0 for byte in range(0, BLOCK_BYTES)]
-    l_a = len(A)//BLOCK_BYTES
-
-    padding_bytes = len(A)%BLOCK_BYTES
-
-    A = ArrayToBlockbytesMatrix(A)
-
-    for i in range(0, l_a) :
-        tweak = TweakAssociatedData(i, padded=False)
-        enc = ltbc.LilliputTBCEnc(tweak, key, A[i])
-        Auth = XorState(Auth, enc)
-
-    if padding_bytes == 0:
-        return Auth
-
-    tweak = TweakAssociatedData(l_a, padded=True)
-    ad_padded = Padding10LSB(A[l_a], padding_bytes*8)
-    enc = ltbc.LilliputTBCEnc(tweak, key, ad_padded)
-    Auth = XorState(Auth, enc)
 
-    return Auth
 
 ################################################################################
 
@@ -214,7 +163,7 @@ def OCB3Enc(A, M, N, key) :
 
     K = list(key)
 
-    Auth = BuildAuth(A, K)
+    Auth = BuildAuth(TWEAK_BITS, A, K)
     (Final, C) = TreatMessageEnc(M, N, K)
     tag = XorState(Auth, Final)
 
@@ -226,7 +175,7 @@ def OCB3Dec(A, C, N, tag, key) :
 
     K = list(key)
 
-    Auth = BuildAuth(A, K)
+    Auth = BuildAuth(TWEAK_BITS, A, K)
     (Final, M) = TreatMessageDec(C, N, K)
     tag2 = XorState(Auth, Final)