ajout crypto

crypto/TP1/Ex2/xtea.c

@@ -0,0 +1,66 @@
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+#define DELTA 0x9E3779B9
+#define ROUNDS 32
+
+void decrypt(uint32_t v[2], uint32_t const key[4]) {
+    uint32_t v0 = v[0], v1 = v[1], sum = DELTA * ROUNDS;
+    for (int i = 0; i < ROUNDS; i++) {
+        v1 -= (((v0 << 4) ^ (v0 >> 5)) + v0) ^ (sum + key[(sum >> 11) & 3]);
+        sum -= DELTA;
+        v0 -= (((v1 << 4) ^ (v1 >> 5)) + v1) ^ (sum + key[sum & 3]);
+    }
+    v[0] = v0;
+    v[1] = v1;
+}
+
+void encrypt(uint32_t v[2], uint32_t const key[4]) {
+    uint32_t v0 = v[0], v1 = v[1], sum = 0;
+    for (int i = 0; i < ROUNDS; i++) {
+        v0 += (((v1 << 4) ^ (v1 >> 5)) + v1) ^ (sum + key[sum & 3]);
+        sum += DELTA;
+        v1 += (((v0 << 4) ^ (v0 >> 5)) + v0) ^ (sum + key[(sum >> 11) & 3]);
+    }
+    v[0] = v0;
+    v[1] = v1;
+}
+
+void process_file(const char *mode, const char *keyfile, const char *inputfile, const char *outputfile) {
+    uint32_t key[4];
+    uint32_t block[2];
+    int fd_key = open(keyfile, O_RDONLY);
+    int fd_in = open(inputfile, O_RDONLY);
+    int fd_out = open(outputfile, O_WRONLY | O_CREAT | O_TRUNC, 0600);
+    
+    if (fd_key < 0 || fd_in < 0 || fd_out < 0) {
+        perror("Error opening file");
+        exit(1);
+    }
+    read(fd_key, key, sizeof(key));
+    close(fd_key);
+    
+    while (read(fd_in, block, sizeof(block)) == sizeof(block)) {
+        if (strcmp(mode, "-d") == 0) {
+            decrypt(block, key);
+        } else {
+            encrypt(block, key);
+        }
+        write(fd_out, block, sizeof(block));
+    }
+    close(fd_in);
+    close(fd_out);
+}
+
+int main(int argc, char *argv[]) {
+    if (argc != 5) {
+        fprintf(stderr, "Usage: %s -e|-d filekey file1 file2\n", argv[0]);
+        return 1;
+    }
+    process_file(argv[1], argv[2], argv[3], argv[4]);
+    return 0;
+}