From 417ac09668ea124245dbac0084608d9c396f5a76 Mon Sep 17 00:00:00 2001
From: Kévin Le Gouguec <kevin.legouguec@airbus.com>
Date: Thu, 14 Mar 2019 16:15:08 +0100
Subject: [implem-python] Retrait de A_BITS/M_BITS (1.5/2)

---
 python/lilliput_ae_2.py | 83 ++++++-------------------------------------------
 1 file changed, 10 insertions(+), 73 deletions(-)

(limited to 'python/lilliput_ae_2.py')

diff --git a/python/lilliput_ae_2.py b/python/lilliput_ae_2.py
index 161598e..164c3df 100644
--- a/python/lilliput_ae_2.py
+++ b/python/lilliput_ae_2.py
@@ -3,7 +3,14 @@
 """
 
 import lilliput_tbc as ltbc
-from helpers import ArrayToBlockbytesMatrix, BlockbytesMatrixToBytes
+from constants import BLOCK_BITS, BLOCK_BYTES
+from helpers import (
+    ArrayToBlockbytesMatrix,
+    BlockbytesMatrixToBytes,
+    BuildAuth,
+    Padding10LSB,
+    XorState
+)
 
 
 BLOCK_BITS = 128
@@ -18,7 +25,6 @@ KEY_BYTES = int(KEY_BITS / 8)
 TWEAK_BYTES = int(TWEAK_BITS / 8)
 TWEAKEY_BYTES = int(TWEAKEY_BITS / 8)
 
-A_BITS = BLOCK_BITS
 M_BITS = BLOCK_BITS
 
 
@@ -38,25 +44,6 @@ 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)) :
@@ -79,48 +66,6 @@ def LowPart(array, number_bits) :
 
     return lower_part_byte
 
-###############################################################################
-
-def TweakAssociatedData(i, padded = 0) :
-    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 padded == 0 :
-        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 = int(A_BITS / BLOCK_BITS)
-    if int(A_BITS % BLOCK_BITS) > 0 :
-        will_padd = 1
-    else :
-        will_padd = 0
-
-    for i in range(0, l_a) :
-        tweak = TweakAssociatedData(i, padded = 0)
-        enc = ltbc.LilliputTBCEnc(tweak, key, A[i])
-        Auth = XorState(Auth, enc)
-
-    if (A_BITS % BLOCK_BITS) == 0 :
-        return Auth
-
-    tweak = TweakAssociatedData(l_a, padded = 1)
-    ad_padded = Padding10LSB(A[l_a], (A_BITS % BLOCK_BITS))
-    enc = ltbc.LilliputTBCEnc(tweak, key, ad_padded)
-    Auth = XorState(Auth, enc)
-
-    return Auth
-
 ################################################################################
 
 def TweakTag(j, padded = 0) :
@@ -211,17 +156,13 @@ def MessageEncryption(M, N, tag, key) :
 def SCT2Enc(A, M, N, key) :
     InitParameters(len(key)*8)
 
-    global A_BITS
     global M_BITS
-
-    A_BITS = len(A)*8
     M_BITS = len(M)*8
 
-    A = ArrayToBlockbytesMatrix(A)
     M = ArrayToBlockbytesMatrix(M)
     K = list(key)
 
-    Auth = BuildAuth(A, K)
+    Auth = BuildAuth(TWEAK_BITS, A, K)
     tag = MesssageAuthTag(M, N, Auth, K)
     C = MessageEncryption(M, N, tag, K)
 
@@ -231,18 +172,14 @@ def SCT2Enc(A, M, N, key) :
 def SCT2Dec(A, C, N, tag, key) :
     InitParameters(len(key)*8)
 
-    global A_BITS
     global M_BITS
-
-    A_BITS = len(A)*8
     M_BITS = len(C)*8
 
-    A = ArrayToBlockbytesMatrix(A)
     C = ArrayToBlockbytesMatrix(C)
     K = list(key)
 
     M = MessageEncryption(C, N, tag, K)
-    Auth = BuildAuth(A, K)
+    Auth = BuildAuth(TWEAK_BITS, A, K)
     tag2 = MesssageAuthTag(M, N, Auth, K)
 
     if(tag == tag2) :
-- 
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