From 3a074358065de5af65510d53f131b98c28f0b547 Mon Sep 17 00:00:00 2001
From: Kévin Le Gouguec <kevin.legouguec@airbus.com>
Date: Mon, 1 Jul 2019 17:00:15 +0200
Subject: Ajout de la multiplication M⁴
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- α₀ devient M
- α₁ M²
- α₂ M³
- α₃ M⁴
- α₄ M_R
- α₅ M_R²
- α₆ M_R³
---
 src/ref/multiplications.h | 20 ++++++++++++++++++++
 src/ref/tweakey.c         |  9 ++++-----
 2 files changed, 24 insertions(+), 5 deletions(-)

(limited to 'src')

diff --git a/src/ref/multiplications.h b/src/ref/multiplications.h
index 4de1848..c0645b9 100644
--- a/src/ref/multiplications.h
+++ b/src/ref/multiplications.h
@@ -71,6 +71,26 @@ static void _multiply_M3(const uint8_t x[LANE_BYTES], uint8_t y[LANE_BYTES])
     y[0] = x[5];
 }
 
+static void _multiply_M4(const uint8_t x[LANE_BYTES], uint8_t y[LANE_BYTES])
+{
+    uint8_t a_5  = x[5]<<3  ^ x[4];
+    uint8_t a_4  = x[4]>>3  ^ x[3];
+    uint8_t b_5 = a_5<<3 ^ a_4;
+    uint8_t b_4 = a_4>>3 ^ x[2];
+
+    uint8_t c_4 = b_4>>3 ^ x[6]<<2 ^ x[1];
+    uint8_t c_5 = b_5<<3 ^ b_4;
+
+    y[7] = b_5;
+    y[6] = c_5;
+    y[5] = c_5<<3 ^ c_4;
+    y[4] = c_4>>3 ^ x[5]<<2 ^ x[0];
+    y[3] = a_5<<2 ^ x[7];
+    y[2] = b_5<<2 ^ x[6];
+    y[1] = x[5];
+    y[0] = a_5;
+}
+
 static void _multiply_MR(const uint8_t x[LANE_BYTES], uint8_t y[LANE_BYTES])
 {
     y[0] = x[1];
diff --git a/src/ref/tweakey.c b/src/ref/tweakey.c
index 2f357ca..510f35a 100644
--- a/src/ref/tweakey.c
+++ b/src/ref/tweakey.c
@@ -63,10 +63,11 @@ void tweakey_state_extract(
 
 typedef void (*matrix_multiplication)(const uint8_t x[LANE_BYTES], uint8_t y[LANE_BYTES]);
 
-static const matrix_multiplication ALPHAS[6] = {
+static const matrix_multiplication ALPHAS[7] = {
     _multiply_M,
     _multiply_M2,
     _multiply_M3,
+    _multiply_M4,
     _multiply_MR,
     _multiply_MR2,
     _multiply_MR3
@@ -75,15 +76,13 @@ static const matrix_multiplication ALPHAS[6] = {
 
 void tweakey_state_update(uint8_t TK[TWEAKEY_BYTES])
 {
-    /* Skip lane 0, as it is multiplied by the identity matrix. */
-
-    for (size_t j=1; j<LANES_NB; j++)
+    for (size_t j=0; j<LANES_NB; j++)
     {
         uint8_t *TKj = TK + j*LANE_BYTES;
 
         uint8_t TKj_old[LANE_BYTES];
         memcpy(TKj_old, TKj, LANE_BYTES);
 
-        ALPHAS[j-1](TKj_old, TKj);
+        ALPHAS[j](TKj_old, TKj);
     }
 }
-- 
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