1 files changed, 83 insertions, 0 deletions
diff --git a/src/tweakey.c b/src/tweakey.c
new file mode 100644
index 0000000..da97019
--- /dev/null
+++ b/src/tweakey.c
@@ -0,0 +1,83 @@
+#include <stdint.h>
+#include <string.h>
+
+#include "constants.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(
+    tweakey_state *TK,
+    const uint8_t key[KEY_BYTES],
+    const uint8_t tweak[TWEAK_BYTES]
+)
+{
+    memcpy(TK->TK,             tweak, TWEAK_BYTES);
+    memcpy(TK->TK+TWEAK_BYTES, key,   KEY_BYTES);
+}
+
+
+void tweakey_state_extract(
+    const tweakey_state *TK,
+    uint8_t round_tweakey[ROUND_TWEAKEY_BYTES], /* output */
+    uint8_t i                                   /* round constant */
+)
+{
+    memset(round_tweakey, 0, ROUND_TWEAKEY_BYTES);
+
+    for (const uint8_t *lane=TK->TK; lane<TK->TK+TWEAKEY_BYTES; lane+=LANE_BYTES)
+    {
+        for (size_t j=0; j<LANE_BYTES; j++)
+        {
+            round_tweakey[j] ^= lane[j];
+        }
+    }
+
+    round_tweakey[0] ^= i;
+}
+
+
+static void _permute_state(tweakey_state *TK)
+{
+    uint8_t TK_old[TWEAKEY_BYTES];
+    memcpy(TK_old, TK->TK, sizeof(TK_old));
+
+    /* TODO: homogenize indices; here j=lane; k=byte */
+
+    for (size_t j=0; j<TWEAKEY_BYTES; j+=LANE_BYTES)
+    {
+        for (size_t k=0; k<LANE_BYTES; k++)
+        {
+            TK->TK[j+h[k]] = TK_old[j+k];
+        }
+    }
+}
+
+static void _multiply_state(tweakey_state *TK)
+{
+    /* Lane 0 is multiplied by Id; lane 1 by P_0, lane 2 by P_1... */
+
+    for (size_t lane=1; lane<LANES_NB; lane++)
+    {
+        const uint8_t* P_lane = P[lane-1];
+
+        /* TODO: homogenize indices; here b=byte */
+
+        for (size_t b=0; b<LANE_BYTES; b++)
+        {
+            size_t offset = lane*LANE_BYTES + b;
+            TK->TK[offset] = P_lane[TK->TK[offset]];
+        }
+    }
+}
+
+void tweakey_state_update(tweakey_state *TK)
+{
+    _permute_state(TK);
+    _multiply_state(TK);
+}