tentative 2eme exo

tp2/spn-decrypt-file.c

@@ -0,0 +1,41 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include "spn.h"
+
+void read_array(const char* filename, unsigned char* array, int size) {
+    FILE* f = fopen(filename, "r");
+    for (int i = 0; i < size; i++) {
+        fscanf(f, "%hhu", &array[i]);
+    }
+    fclose(f);
+}
+
+int main(int argc, char* argv[]) {
+    if (argc != 6) {
+        printf("%s <key_file> <subst_file> <perm_file> <input> <output>\n", argv[0]);
+        return 1;
+    }
+
+    FILE* fkey = fopen(argv[1], "r");
+    unsigned int key;
+    fscanf(fkey, "%u", &key);
+    fclose(fkey);
+
+    unsigned char subst[16], perm[16];
+    read_array(argv[2], subst, 16);
+    read_array(argv[3], perm, 16);
+
+    FILE* fin = fopen(argv[4], "rb");
+    FILE* fout = fopen(argv[5], "wb");
+
+    unsigned short block;
+    while (fread(&block, 2, 1, fin)) {
+        unsigned short dec = decrypt(block, key, perm, subst);
+        fputc(dec >> 8, fout);
+        fputc(dec & 0xFF, fout);
+    }
+
+    fclose(fin);
+    fclose(fout);
+    return 0;
+}

tp2/spn-encrypt-file.c

@@ -0,0 +1,44 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include "spn.h"
+
+void read_array(const char* filename, unsigned char* array, int size) {
+    FILE* f = fopen(filename, "r");
+    for (int i = 0; i < size; i++) {
+        fscanf(f, "%hhu", &array[i]);
+    }
+    fclose(f);
+}
+
+int main(int argc, char* argv[]) {
+    if (argc != 6) {
+        printf("%s <key_file> <subst_file> <perm_file> <input> <output>\n", argv[0]);
+        return 1;
+    }
+
+    FILE* fkey = fopen(argv[1], "r");
+    unsigned int key;
+    fscanf(fkey, "%u", &key);
+    fclose(fkey);
+
+    unsigned char subst[16], perm[16];
+    read_array(argv[2], subst, 16);
+    read_array(argv[3], perm, 16);
+
+    FILE* fin = fopen(argv[4], "rb");
+    FILE* fout = fopen(argv[5], "wb");
+
+    unsigned char b1, b2;
+    while (fread(&b1, 1, 1, fin)) {
+        if (fread(&b2, 1, 1, fin) != 1) {
+            b2 = 0; 
+        }
+        unsigned short block = (b1 << 8) | b2;
+        unsigned short enc = encrypt(block, key, perm, subst);
+        fwrite(&enc, 2, 1, fout);
+    }
+
+    fclose(fin);
+    fclose(fout);
+    return 0;
+}

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 encrypt(unsigned short w, unsigned int   key, unsigned char  perm[16], unsigned char  subst[16]) {
-    unsigned short result = 0;
+    for (int i = 0; i < 2; i++) {
-    for (int i = 0; i < 16; i++) {
+        unsigned char rk = (key >> (8 * (3 - i))) & 0xFF;
-        if ((w >> i) & 1)
+        w ^= (rk << 8) | rk;
-            result |= (1 << perm[i]);
+
+        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;
-}
-
-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));
-    }
-    return result;
-}
-
-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 decrypt(unsigned short w, unsigned int   key, unsigned char  perm[16], unsigned char  subst[16]) {
-    unsigned short w,
+    unsigned char inverseSubst[16];
-    unsigned int key,
+    unsigned char inversePerm[16];
-    unsigned char perm[16],
+    for (int i = 0; i < 16; ++i) {
-    unsigned char subst[16]
+        inverseSubst[subst[i]] = i;
-) {
+        inversePerm[perm [i]] = i;
-    // 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;
     }
 
+    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; 
 }