lilliput-ae-reference-implementation

commit 4a89a70f14703e9a45eb490b44ca7621a516da71
parent 4e5d619a69aa79c61986ce3b4ee86486e583eab3
Author: Kévin Le Gouguec <kevin.legouguec@airbus.com>
Date:   Mon,  3 Dec 2018 15:28:58 +0100

Nettoyage des indices dans l'implémentation du key schedule

Idéalement,  il faudrait  que  j  ne soit  plus  utilisé comme  indice
d'octet dans la spécification.

Diffstat:
M
src/tweakey.c
 | 
23
++++++++++++++---------

1 file changed, 14 insertions(+), 9 deletions(-)
diff --git a/src/tweakey.c b/src/tweakey.c
@@ -8,7 +8,7 @@
 
 #define LANE_BITS  64
 #define LANE_BYTES (LANE_BITS/8)
-#define LANES_NB (TWEAKEY_BYTES/LANE_BYTES)
+#define LANES_NB   (TWEAKEY_BYTES/LANE_BYTES)
 
 
 void tweakey_state_init(
@@ -30,11 +30,13 @@ void tweakey_state_extract(
 {
     memset(round_tweakey, 0, ROUND_TWEAKEY_BYTES);
 
-    for (const uint8_t *lane=TK; lane<TK+TWEAKEY_BYTES; lane+=LANE_BYTES)
+    for (size_t j=0; j<LANES_NB; j++)
     {
-        for (size_t j=0; j<LANE_BYTES; j++)
+        const uint8_t *TKj = TK + j*LANE_BYTES;
+
+        for (size_t k=0; k<LANE_BYTES; k++)
         {
-            round_tweakey[j] ^= lane[j];
+            round_tweakey[k] ^= TKj[k];
         }
     }
 
@@ -47,11 +49,14 @@ static void _permute_state(uint8_t TK[TWEAKEY_BYTES])
     uint8_t TK_old[TWEAKEY_BYTES];
     memcpy(TK_old, TK, TWEAKEY_BYTES);
 
-    for (size_t j=0; j<TWEAKEY_BYTES; j+=LANE_BYTES)
+    for (size_t j=0; j<LANES_NB; j++)
     {
+        uint8_t       *TKj     = TK     + j*LANE_BYTES;
+        uint8_t const *TKj_old = TK_old + j*LANE_BYTES;
+
         for (size_t k=0; k<LANE_BYTES; k++)
         {
-            TK[j+h[k]] = TK_old[j+k];
+            TKj[h[k]] = TKj_old[k];
         }
     }
 }
@@ -70,12 +75,12 @@ static void _multiply_state(uint8_t TK[TWEAKEY_BYTES])
 
     for (size_t j=1; j<LANES_NB; j++)
     {
-        const uint8_t *P_j = P[j-1];
+        uint8_t const *Pj  = P[j-1];
+        uint8_t       *TKj = TK + j*LANE_BYTES;
 
         for (size_t k=0; k<LANE_BYTES; k++)
         {
-            size_t offset = j*LANE_BYTES + k;
-            TK[offset] = P_j[TK[offset]];
+            TKj[k] = Pj[TKj[k]];
         }
     }
 }