DES-CTR模式C语言代码
时间: 2023-07-10 15:37:08 浏览: 85
以下为DES-CTR模式的C语言代码示例:
```c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <openssl/des.h>
#define BLOCK_SIZE 8
void increment_iv(unsigned char *iv) {
int i;
for (i = BLOCK_SIZE - 1; i >= 0; i--) {
if (iv[i] == 0xff) {
iv[i] = 0;
} else {
iv[i]++;
break;
}
}
}
void des_ctr_encrypt(unsigned char *plaintext, unsigned char *ciphertext,
long plaintext_len, unsigned char *key,
unsigned char *iv) {
DES_key_schedule key_schedule;
DES_set_key_checked(key, &key_schedule);
unsigned char keystream[BLOCK_SIZE];
unsigned char block[BLOCK_SIZE];
int i, j;
for (i = 0; i < plaintext_len; i += BLOCK_SIZE) {
DES_ecb_encrypt(iv, keystream, &key_schedule, DES_ENCRYPT);
for (j = 0; j < BLOCK_SIZE; j++) {
block[j] = plaintext[i + j] ^ keystream[j];
ciphertext[i + j] = block[j];
}
increment_iv(iv);
}
}
void des_ctr_decrypt(unsigned char *ciphertext, unsigned char *plaintext,
long ciphertext_len, unsigned char *key,
unsigned char *iv) {
DES_key_schedule key_schedule;
DES_set_key_checked(key, &key_schedule);
unsigned char keystream[BLOCK_SIZE];
unsigned char block[BLOCK_SIZE];
int i, j;
for (i = 0; i < ciphertext_len; i += BLOCK_SIZE) {
DES_ecb_encrypt(iv, keystream, &key_schedule, DES_ENCRYPT);
for (j = 0; j < BLOCK_SIZE; j++) {
block[j] = ciphertext[i + j] ^ keystream[j];
plaintext[i + j] = block[j];
}
increment_iv(iv);
}
}
int main() {
unsigned char key[] = "01234567";
unsigned char iv[] = "12345678";
unsigned char plaintext[] = "Hello, DES-CTR!";
long plaintext_len = strlen((char *) plaintext);
unsigned char ciphertext[plaintext_len];
des_ctr_encrypt(plaintext, ciphertext, plaintext_len, key, iv);
printf("Ciphertext: %s\n", ciphertext);
unsigned char decrypted[plaintext_len];
des_ctr_decrypt(ciphertext, decrypted, plaintext_len, key, iv);
printf("Plaintext: %s\n", decrypted);
return 0;
}
```
注意:此处的DES算法使用了OpenSSL库。在使用此代码时需要在编译命令中添加-lcrypto选项。
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