From 7350fbb6583236b929235a8be7f17f149901f004 Mon Sep 17 00:00:00 2001
From: Kévin Le Gouguec <kevin.legouguec@airbus.com>
Date: Thu, 21 Mar 2019 17:16:21 +0100
Subject: [implem-python] Simplification de pad10*
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Dans le cadre d'une croisade contre les range(len(…)).

Suppression d'un paramètre inutile dans la foulée.
---
 python/helpers.py       | 23 ++++++-----------------
 python/lilliput_ae_1.py |  4 ++--
 python/lilliput_ae_2.py | 10 +++++-----
 3 files changed, 13 insertions(+), 24 deletions(-)

diff --git a/python/helpers.py b/python/helpers.py
index 07affa9..be4b406 100644
--- a/python/helpers.py
+++ b/python/helpers.py
@@ -32,19 +32,9 @@ def XorState(state1, state2):
     return [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 Padding10LSB(X):
+    zeroes = [0] * (BLOCK_BYTES-len(X)-1)
+    return zeroes + [0b10000000] + X
 
 
 def _tweakAssociatedData(t, i, padded):
@@ -69,8 +59,7 @@ def _tweakAssociatedData(t, i, padded):
 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
+    need_padding = len(A)%BLOCK_BYTES > 0
 
     A = ArrayToBlockbytesMatrix(A)
 
@@ -79,11 +68,11 @@ def BuildAuth(t, A, key):
         enc = LilliputTBCEnc(tweak, key, A[i])
         Auth = XorState(Auth, enc)
 
-    if padding_bytes == 0:
+    if not need_padding:
         return Auth
 
     tweak = _tweakAssociatedData(t, l_a, padded=True)
-    ad_padded = Padding10LSB(A[l_a], padding_bytes*8)
+    ad_padded = Padding10LSB(A[l_a])
     enc = LilliputTBCEnc(tweak, key, ad_padded)
     Auth = XorState(Auth, enc)
 
diff --git a/python/lilliput_ae_1.py b/python/lilliput_ae_1.py
index 0bc4236..5cc263b 100644
--- a/python/lilliput_ae_1.py
+++ b/python/lilliput_ae_1.py
@@ -85,7 +85,7 @@ def TreatMessageEnc(M, N, key):
         Final = ltbc.LilliputTBCEnc(tweak, key, checksum)
 
     else:
-        m_padded = Padding10LSB(M[l], padding_bytes*8)
+        m_padded = Padding10LSB(M[l])
         checksum = XorState(checksum, m_padded)
         tweak = TweakMessage(N, l, _MessageTweak.PAD)
         pad = ltbc.LilliputTBCEnc(tweak, key, [0 for byte in range(0, BLOCK_BYTES)])
@@ -122,7 +122,7 @@ def TreatMessageDec(C, N, key):
         lower_part = LowPart(pad, padding_bytes*8)
         M.append(XorState(C[l], lower_part))
 
-        m_padded = Padding10LSB(M[l], padding_bytes*8)
+        m_padded = Padding10LSB(M[l])
         checksum = XorState(checksum, m_padded)
         tweak_final = TweakMessage(N, l+1, _MessageTweak.FINAL)
         Final = ltbc.LilliputTBCEnc(tweak_final, key, checksum)
diff --git a/python/lilliput_ae_2.py b/python/lilliput_ae_2.py
index 3f72020..2e7843b 100644
--- a/python/lilliput_ae_2.py
+++ b/python/lilliput_ae_2.py
@@ -55,7 +55,7 @@ def AddTagJ(tag, j):
 
 def MesssageAuthTag(M, N, Auth, key):
     l = len(M)//BLOCK_BYTES
-    padding_bytes = len(M)%BLOCK_BYTES
+    need_padding = len(M)%BLOCK_BYTES > 0
 
     tag = list(Auth)
     M = ArrayToBlockbytesMatrix(M)
@@ -65,9 +65,9 @@ def MesssageAuthTag(M, N, Auth, key):
         encryption = ltbc.LilliputTBCEnc(tweak, key, M[j])
         tag = XorState(tag, encryption)
 
-    if padding_bytes > 0:
+    if need_padding:
         tweak = TweakTag(l, True)
-        m_padded = Padding10LSB(M[l], 8*padding_bytes)
+        m_padded = Padding10LSB(M[l])
         encryption = ltbc.LilliputTBCEnc(tweak, key, m_padded)
         tag = XorState(tag, encryption)
 
@@ -80,7 +80,7 @@ def MesssageAuthTag(M, N, Auth, key):
 
 def MessageEncryption(M, N, tag, key):
     l = len(M)//BLOCK_BYTES
-    padding_bytes = len(M)%BLOCK_BYTES
+    need_padding = len(M)%BLOCK_BYTES > 0
 
     M = ArrayToBlockbytesMatrix(M)
     C = []
@@ -91,7 +91,7 @@ def MessageEncryption(M, N, tag, key):
         encryption = ltbc.LilliputTBCEnc(tweak, key, padded_nonce)
         C.append(XorState(M[j], encryption))
 
-    if padding_bytes > 0:
+    if need_padding:
         tweak = AddTagJ(tag, l)
         padded_nonce = list(N) + [0x00]
         encryption = ltbc.LilliputTBCEnc(tweak, key, padded_nonce)
-- 
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