ajout crypto

crypto/TP1/Ex1/file.txt

@@ -0,0 +1,16 @@
+Demain, dès l'aube, à l'heure où blanchit la campagne,
+Je partirai. Vois-tu, je sais que tu m'attends.
+J'irai par la forêt, j'irai par la montagne.
+Je ne puis demeurer loin de toi plus longtemps.
+
+Je marcherai les yeux fixés sur mes pensées,
+Sans rien voir au dehors, sans entendre aucun bruit,
+Seul, inconnu, le dos courbé, les mains croisées,
+Triste, et le jour pour moi sera comme la nuit.
+
+Je ne regarderai ni l'or du soir qui tombe,
+Ni les voiles au loin descendant vers Harfleur,
+Et quand j'arriverai, je mettrai sur ta tombe
+Un bouquet de houx vert et de bruyère en fleur.
+
+— Victor Hugo, Les Contemplations, 3 septembre 1847

crypto/TP1/Ex1/lfsr.c

@@ -0,0 +1,43 @@
+#include <stdio.h>
+#include <assert.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+#define MASK_BIT_7      0x80
+#define MASK_BIT_6      0x40
+#define MASK_BIT_5      0x20
+#define MASK_BIT_4      0x10
+#define MASK_BIT_3      0x08
+#define MASK_BIT_2      0x04
+#define MASK_BIT_1      0x02
+#define MASK_BIT_0      0x01
+
+
+unsigned char next(unsigned char lfsr)
+{
+	unsigned char new_bit = __builtin_parity(lfsr & (MASK_BIT_7 | MASK_BIT_6 | MASK_BIT_5 | MASK_BIT_4 | MASK_BIT_3 | MASK_BIT_1));
+    return (lfsr << 1) | new_bit;
+}
+
+int main(int argc, char *argv[])
+{
+	int fd_in,fd_out;
+	unsigned char w,buf;;
+
+
+	assert(argc >= 4);
+	fd_in = open(argv[1],O_RDONLY);
+	fd_out = open(argv[2],O_WRONLY|O_TRUNC|O_CREAT,0600);
+	w = (unsigned char)strtol(argv[3],NULL,0);
+
+	while(1){
+		ssize_t nb = read(fd_in,&buf,1);
+		if (nb <=0)
+			break;
+		buf ^= w;
+		write(fd_out,&buf,1);
+		w=next(w);
+	}
+	return 0;
+}

crypto/TP1/Ex2/key1.k

@@ -0,0 +1 @@
+÷Nà{q2‘*:¬¨œÇmfU#©`í±Å?&Q3

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;
+}

crypto/TP1/Ex3/Xtea_hash.c

@@ -0,0 +1,64 @@
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#define DELTA 0x9E3779B9
+#define ROUNDS 32
+#define BLOCK_SIZE 24
+
+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 xtea_hash(const char *filename, uint64_t *hash) {
+    int fd = open(filename, O_RDONLY);
+    if (fd < 0) {
+        perror("Error opening file");
+        exit(1);
+    }
+    
+    uint64_t current_hash = 0;
+    uint8_t buffer[BLOCK_SIZE];
+    ssize_t bytes_read;
+    
+    while ((bytes_read = read(fd, buffer, BLOCK_SIZE)) > 0) {
+        if (bytes_read < BLOCK_SIZE) {
+            memset(buffer + bytes_read, 0, BLOCK_SIZE - bytes_read);
+            buffer[BLOCK_SIZE - 1] = BLOCK_SIZE - bytes_read;
+        }
+        
+        uint32_t x[2];
+        uint32_t k[4];
+        memcpy(x, buffer, 8);
+        memcpy(k, buffer + 8, 16);
+        
+        encrypt(x, k);
+        uint64_t hashed_block = ((uint64_t)x[0] << 32) | x[1];
+        current_hash ^= hashed_block;
+    }
+    
+    close(fd);
+    *hash = current_hash;
+}
+
+int main(int argc, char *argv[]) {
+    if (argc != 2) {
+        fprintf(stderr, "Usage: %s <file>\n", argv[0]);
+        return 1;
+    }
+    
+    uint64_t hash;
+    xtea_hash(argv[1], &hash);
+    printf("Hash: %016lx\n", hash);
+    return 0;
+}