83 lines
2.2 KiB
C
83 lines
2.2 KiB
C
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#include <stdint.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#define DELTA 0x9E3779B9
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void xtea_encrypt_block(uint32_t *v, const uint32_t key[4]) {
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uint32_t v0 = v[0], v1 = v[1], sum = 0;
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for (unsigned i = 0; i < 32; i++) {
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v0 += (((v1 << 4) ^ (v1 >> 5)) + v1) ^ (sum + key[sum & 3]);
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sum += DELTA;
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v1 += (((v0 << 4) ^ (v0 >> 5)) + v0) ^ (sum + key[(sum >> 11) & 3]);
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}
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v[0] = v0;
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v[1] = v1;
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}
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void xtea_decrypt_block(uint32_t *v, const uint32_t key[4]) {
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uint32_t v0 = v[0], v1 = v[1];
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uint32_t sum = DELTA * 32;
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for (unsigned i = 0; i < 32; i++) {
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v1 -= (((v0 << 4) ^ (v0 >> 5)) + v0) ^ (sum + key[(sum >> 11) & 3]);
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sum -= DELTA;
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v0 -= (((v1 << 4) ^ (v1 >> 5)) + v1) ^ (sum + key[sum & 3]);
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}
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v[0] = v0;
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v[1] = v1;
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}
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void xtea_process(int encrypt, const char *keyfile, const char *infile, const char *outfile) {
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uint32_t key[4];
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FILE *fk = fopen(keyfile, "rb");
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if (!fk || fread(key, sizeof *key, 4, fk) != 4) {
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fprintf(stderr, "Erreur lecture clé\n");
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exit(1);
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}
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fclose(fk);
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FILE *fin = fopen(infile, "rb");
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FILE *fout = fopen(outfile, "wb");
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if (!fin || !fout) {
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fprintf(stderr, "Erreur ouverture fichiers\n");
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exit(1);
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}
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uint8_t block[8];
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size_t n;
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while ((n = fread(block, 1, 8, fin)) == 8) {
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xtea_encrypt_block((uint32_t*)block, key);
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if (!encrypt)
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xtea_decrypt_block((uint32_t*)block, key);
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fwrite(block, 1, 8, fout);
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}
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if (encrypt) {
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for (size_t i = n; i < 8 - 1; i++) {
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block[i] = 0;
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}
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block[8 - 1] = 8 - n;
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xtea_encrypt_block((uint32_t*)block, key);
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fwrite(block, 1, 8, fout);
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} else if (n > 0) {
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fprintf(stderr, "Erreur : fichier chiffré mal aligné\n");
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exit(1);
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}
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fclose(fin);
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fclose(fout);
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}
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int main(int argc, char *argv[])
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{
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if (argc != 5) {
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fprintf(stderr, "Usage : %s -e|-d keyfile infile outfile\n", argv[0]);
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return 1;
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}
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int enc = (strcmp(argv[1], "-e") == 0);
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xtea_process(enc, argv[2], argv[3], argv[4]);
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return 0;
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}
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