tentative 2eme exo

tp2/spn.c

@@ -6,81 +6,59 @@ unsigned char do_subst(unsigned char w, unsigned char subst[16]) {
 
 unsigned char do_perm(unsigned char w, unsigned char perm[16]) {
     unsigned char result = 0;
-    for (int i = 0; i < 8; i++) {
+    for (int i = 0; i < 8; i++)
         if ((w >> i) & 1)
             result |= (1 << perm[i]);
-    }
     return result;
 }
 
-unsigned short apply_perm16(unsigned short w, unsigned char perm[16]) {
-    unsigned short result = 0;
-    for (int i = 0; i < 16; i++) {
-        if ((w >> i) & 1)
-            result |= (1 << perm[i]);
+unsigned short encrypt(unsigned short w, unsigned int   key, unsigned char  perm[16], unsigned char  subst[16]) {
+    for (int i = 0; i < 2; i++) {
+        unsigned char rk = (key >> (8 * (3 - i))) & 0xFF;
+        w ^= (rk << 8) | rk;
+
+        unsigned short tmp = 0;
+        for (int j = 0; j < 4; ++j) {
+            unsigned char nib = (w >> (j * 4)) & 0xF;
+            tmp |= (subst[nib] << (j * 4));
+        }
+        w = tmp;
+
+        unsigned short permute = 0;
+        for (int j = 0; j < 16; ++j)
+            if ((w >> j) & 1) {
+                permute |= (1 << perm[j]);
+            }
+        w = permute;
     }
-    return result;
+    return w;     
 }
 
-unsigned short apply_subst16(unsigned short w, unsigned char subst[16]) {
-    unsigned short result = 0;
-    for (int i = 0; i < 4; i++) {
-        unsigned char nibble = (w >> (i * 4)) & 0xF;
-        result |= (do_subst(nibble, subst) << (i * 4));
+unsigned short decrypt(unsigned short w, unsigned int   key, unsigned char  perm[16], unsigned char  subst[16]) {
+    unsigned char inverseSubst[16];
+    unsigned char inversePerm[16];
+    for (int i = 0; i < 16; ++i) {
+        inverseSubst[subst[i]] = i;
+        inversePerm[perm [i]] = i;
     }
-    return result;
+
+    for (int i = 1; i >= 0; --i) {
+        unsigned short permInverse = 0;
+        for (int j = 0; j < 16; ++j)
+            if ((w >> j) & 1) {
+                permInverse |= (1 << inversePerm[j]);
+            }
+        w = permInverse;
+
+        unsigned short tmp = 0;
+        for (int j = 0; j < 4; ++j) {
+            unsigned char sousBloc = (w >> (j * 4)) & 0xF;
+            tmp |= (inverseSubst[sousBloc] << (j * 4));
+        }
+        w = tmp;
+
+        unsigned char rk = (key >> (8 * (3 - i))) & 0xFF;
+        w ^= (rk << 8) | rk;
+    }
+    return w; 
 }
-
-unsigned short encrypt(
-    unsigned short w,
-    unsigned int key,
-    unsigned char perm[16],
-    unsigned char subst[16]
-) {
-    for (int round = 0; round < 2; round++) {
-        unsigned char round_key = (key >> (8 * (3 - round))) & 0xFF;
-        w ^= (round_key << 8) | round_key;
-
-        w = apply_subst16(w, subst);
-        w = apply_perm16(w, perm);
-    }
-
-    // Dernier round - pas de permutation
-    unsigned char round_key = (key & 0xFF);
-    w ^= (round_key << 8) | round_key;
-    w = apply_subst16(w, subst);
-
-    return w;
-}
-
-unsigned short decrypt(
-    unsigned short w,
-    unsigned int key,
-    unsigned char perm[16],
-    unsigned char subst[16]
-) {
-    // Inverser la substitution
-    unsigned char inv_subst[16];
-    for (int i = 0; i < 16; i++)
-        inv_subst[subst[i]] = i;
-
-    // Inverser la permutation
-    unsigned char inv_perm[16];
-    for (int i = 0; i < 16; i++)
-        inv_perm[perm[i]] = i;
-
-    // Dernier tour
-    w = apply_subst16(w, inv_subst);
-    unsigned char round_key = (key & 0xFF);
-    w ^= (round_key << 8) | round_key;
-
-    // 2 tours inverses
-    for (int round = 1; round >= 0; round--) {
-        w = apply_perm16(w, inv_perm);
-        w = apply_subst16(w, inv_subst);
-        round_key = (key >> (8 * (3 - round))) & 0xFF;
-        w ^= (round_key << 8) | round_key;
-    }
-
-    return w;
-}