From f403a3a70574c1cfe80efbba39f09fe4853e2ab9 Mon Sep 17 00:00:00 2001
From: Kévin Le Gouguec <kevin.legouguec@airbus.com>
Date: Wed, 12 Dec 2018 08:54:57 +0100
Subject: Ajout d'une version alternative du key schedule
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Dans cette version, les multiplications par Mⁱ (resp. MRⁱ) sont faites
en  appliquant  M (resp.   MR)  i  fois,  plutôt qu'en  utilisant  les
expressions données dans la spécification.
---
 src/tweakey-unrolled-multiplications.c | 127 +++++++++++++++++++++++++++++++++
 1 file changed, 127 insertions(+)
 create mode 100644 src/tweakey-unrolled-multiplications.c

diff --git a/src/tweakey-unrolled-multiplications.c b/src/tweakey-unrolled-multiplications.c
new file mode 100644
index 0000000..54b3036
--- /dev/null
+++ b/src/tweakey-unrolled-multiplications.c
@@ -0,0 +1,127 @@
+#include <stdint.h>
+#include <string.h>
+
+#include "parameters.h"
+#include "tweakey.h"
+
+
+#define LANE_BITS  64
+#define LANE_BYTES (LANE_BITS/8)
+#define LANES_NB   (TWEAKEY_BYTES/LANE_BYTES)
+
+
+void tweakey_state_init(
+    uint8_t TK[TWEAKEY_BYTES],
+    const uint8_t key[KEY_BYTES],
+    const uint8_t tweak[TWEAK_BYTES]
+)
+{
+    memcpy(TK,             tweak, TWEAK_BYTES);
+    memcpy(TK+TWEAK_BYTES, key,   KEY_BYTES);
+}
+
+
+void tweakey_state_extract(
+    const uint8_t TK[TWEAKEY_BYTES],
+    uint8_t round_constant,
+    uint8_t round_tweakey[ROUND_TWEAKEY_BYTES]
+)
+{
+    memset(round_tweakey, 0, ROUND_TWEAKEY_BYTES);
+
+    for (size_t j=0; j<LANES_NB; j++)
+    {
+        const uint8_t *TKj = TK + j*LANE_BYTES;
+
+        for (size_t k=0; k<LANE_BYTES; k++)
+        {
+            round_tweakey[k] ^= TKj[k];
+        }
+    }
+
+    round_tweakey[0] ^= round_constant;
+}
+
+
+static void _multiply_M(const uint8_t X[LANE_BYTES], uint8_t Y[LANE_BYTES])
+{
+    Y[7] = X[6];
+    Y[6] = X[5];
+    Y[5] = X[5]<<3 ^ X[4];
+    Y[4] = X[4]>>3 ^ X[3];
+    Y[3] = X[2];
+    Y[2] = X[6]<<2 ^ X[1];
+    Y[1] = X[0];
+    Y[0] = X[7];
+}
+
+static void _multiply_M2(const uint8_t X[LANE_BYTES], uint8_t Y[LANE_BYTES])
+{
+    uint8_t M_X[LANE_BYTES];
+    _multiply_M(X, M_X);
+    _multiply_M(M_X, Y);
+}
+
+static void _multiply_M3(const uint8_t X[LANE_BYTES], uint8_t Y[LANE_BYTES])
+{
+    uint8_t M_X[LANE_BYTES];
+    uint8_t M2_X[LANE_BYTES];
+    _multiply_M(X, M_X);
+    _multiply_M(M_X, M2_X);
+    _multiply_M(M2_X, Y);
+}
+
+static void _multiply_MR(const uint8_t X[LANE_BYTES], uint8_t Y[LANE_BYTES])
+{
+    Y[0] = X[1];
+    Y[1] = X[2];
+    Y[2] = X[3]    ^ X[4]>>3;
+    Y[3] = X[4];
+    Y[4] = X[5]    ^ X[6]<<3;
+    Y[5] = X[3]<<2 ^ X[6];
+    Y[6] = X[7];
+    Y[7] = X[0];
+}
+
+static void _multiply_MR2(const uint8_t X[LANE_BYTES], uint8_t Y[LANE_BYTES])
+{
+    uint8_t MR_X[LANE_BYTES];
+    _multiply_MR(X, MR_X);
+    _multiply_MR(MR_X, Y);
+}
+
+static void _multiply_MR3(const uint8_t X[LANE_BYTES], uint8_t Y[LANE_BYTES])
+{
+    uint8_t MR_X[LANE_BYTES];
+    uint8_t MR2_X[LANE_BYTES];
+    _multiply_MR(X, MR_X);
+    _multiply_MR(MR_X, MR2_X);
+    _multiply_MR(MR2_X, Y);
+}
+
+typedef void (*matrix_multiplication)(const uint8_t X[LANE_BYTES], uint8_t Y[LANE_BYTES]);
+
+static const matrix_multiplication ALPHAS[6] = {
+    _multiply_M,
+    _multiply_M2,
+    _multiply_M3,
+    _multiply_MR,
+    _multiply_MR2,
+    _multiply_MR3
+};
+
+
+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++)
+    {
+        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);
+    }
+}
-- 
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