Pré-calcul de M²

Les tests passent, c'est encourageant.

1 files changed, 43 insertions, 5 deletions

diff --git a/src/tweakey.c b/src/tweakey.c
index c7d5aaa..d202dc4 100644
--- a/src/tweakey.c
+++ b/src/tweakey.c
@@ -55,13 +55,51 @@ static void _multiply_M(const uint8_t old[LANE_BYTES], uint8_t new[LANE_BYTES])
     new[0] = old[7];
 }
 
+static const uint8_t M_1[256] = {
+    0x00, 0x08, 0x10, 0x18, 0x20, 0x28, 0x30, 0x38,
+    0x41, 0x49, 0x51, 0x59, 0x61, 0x69, 0x71, 0x79,
+    0x82, 0x8a, 0x92, 0x9a, 0xa2, 0xaa, 0xb2, 0xba,
+    0xc3, 0xcb, 0xd3, 0xdb, 0xe3, 0xeb, 0xf3, 0xfb,
+    0x04, 0x0c, 0x14, 0x1c, 0x24, 0x2c, 0x34, 0x3c,
+    0x45, 0x4d, 0x55, 0x5d, 0x65, 0x6d, 0x75, 0x7d,
+    0x86, 0x8e, 0x96, 0x9e, 0xa6, 0xae, 0xb6, 0xbe,
+    0xc7, 0xcf, 0xd7, 0xdf, 0xe7, 0xef, 0xf7, 0xff,
+    0x08, 0x00, 0x18, 0x10, 0x28, 0x20, 0x38, 0x30,
+    0x49, 0x41, 0x59, 0x51, 0x69, 0x61, 0x79, 0x71,
+    0x8a, 0x82, 0x9a, 0x92, 0xaa, 0xa2, 0xba, 0xb2,
+    0xcb, 0xc3, 0xdb, 0xd3, 0xeb, 0xe3, 0xfb, 0xf3,
+    0x0c, 0x04, 0x1c, 0x14, 0x2c, 0x24, 0x3c, 0x34,
+    0x4d, 0x45, 0x5d, 0x55, 0x6d, 0x65, 0x7d, 0x75,
+    0x8e, 0x86, 0x9e, 0x96, 0xae, 0xa6, 0xbe, 0xb6,
+    0xcf, 0xc7, 0xdf, 0xd7, 0xef, 0xe7, 0xff, 0xf7,
+    0x10, 0x18, 0x00, 0x08, 0x30, 0x38, 0x20, 0x28,
+    0x51, 0x59, 0x41, 0x49, 0x71, 0x79, 0x61, 0x69,
+    0x92, 0x9a, 0x82, 0x8a, 0xb2, 0xba, 0xa2, 0xaa,
+    0xd3, 0xdb, 0xc3, 0xcb, 0xf3, 0xfb, 0xe3, 0xeb,
+    0x14, 0x1c, 0x04, 0x0c, 0x34, 0x3c, 0x24, 0x2c,
+    0x55, 0x5d, 0x45, 0x4d, 0x75, 0x7d, 0x65, 0x6d,
+    0x96, 0x9e, 0x86, 0x8e, 0xb6, 0xbe, 0xa6, 0xae,
+    0xd7, 0xdf, 0xc7, 0xcf, 0xf7, 0xff, 0xe7, 0xef,
+    0x18, 0x10, 0x08, 0x00, 0x38, 0x30, 0x28, 0x20,
+    0x59, 0x51, 0x49, 0x41, 0x79, 0x71, 0x69, 0x61,
+    0x9a, 0x92, 0x8a, 0x82, 0xba, 0xb2, 0xaa, 0xa2,
+    0xdb, 0xd3, 0xcb, 0xc3, 0xfb, 0xf3, 0xeb, 0xe3,
+    0x1c, 0x14, 0x0c, 0x04, 0x3c, 0x34, 0x2c, 0x24,
+    0x5d, 0x55, 0x4d, 0x45, 0x7d, 0x75, 0x6d, 0x65,
+    0x9e, 0x96, 0x8e, 0x86, 0xbe, 0xb6, 0xae, 0xa6,
+    0xdf, 0xd7, 0xcf, 0xc7, 0xff, 0xf7, 0xef, 0xe7
+};
+
 static void _multiply_M2(const uint8_t old[LANE_BYTES], uint8_t new[LANE_BYTES])
 {
-    uint8_t tmp[LANE_BYTES];
-    memcpy(tmp, old, LANE_BYTES);
-
-    _multiply_M(old, tmp);
-    _multiply_M(tmp, new);
+    new[7] = old[5];
+    new[6] = old[4]    ^ old[5]<<3;
+    new[5] = old[3]    ^ M_1[old[4]] ^ old[5]<<6;
+    new[4] = old[2]    ^ old[3]>>3   ^ old[4]>>6;
+    new[3] = old[6]<<2 ^ old[1];
+    new[2] = old[5]<<2 ^ old[0];
+    new[1] = old[7];
+    new[0] = old[6];
 }
 
 static void _multiply_M3(const uint8_t old[LANE_BYTES], uint8_t new[LANE_BYTES])