1 files changed, 11 insertions, 3 deletions
diff --git a/src/tweakey.c b/src/tweakey.c
index 761ec53..d1893e0 100644
--- a/src/tweakey.c
+++ b/src/tweakey.c
@@ -58,16 +58,24 @@ static void _permute_state(uint8_t TK[TWEAKEY_BYTES])
 
 static void _multiply_state(uint8_t TK[TWEAKEY_BYTES])
 {
-    /* Lane 0 is multiplied by Id; lane 1 by P_0, lane 2 by P_1... */
+    /* Each byte in lane 0 is multiplied by alpha_0 = 1, i.e. it
+     * remains unchanged.
+     *
+     * Each byte b in lanes j = { 1, ..., p-1 } is multiplied by
+     * alpha_j; the result of b*alpha_j is stored in P_j[b].
+     *
+     * In this implementation, P_j sequences are stored in array P;
+     * P_j = P[j-1].
+     */
 
     for (size_t j=1; j<LANES_NB; j++)
     {
-        const uint8_t *P_lane = P[j-1];
+        const uint8_t *P_j = P[j-1];
 
         for (size_t k=0; k<LANE_BYTES; k++)
         {
             size_t offset = j*LANE_BYTES + k;
-            TK[offset] = P_lane[TK[offset]];
+            TK[offset] = P_j[TK[offset]];
         }
     }
 }