AES Encrypt and Decrypt example code in C Programming

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

/*

* MCrypt API available online:

* http://linux.die.net/man/3/mcrypt

*/

#include <mcrypt.h>

#include <math.h>

#include <stdint.h>

#include <stdlib.h>

int encrypt(

void* buffer,

int buffer_len, /* Because the plaintext could include null bytes*/

char* IV,

char* key,

int key_len

){

MCRYPT td = mcrypt_module_open("rijndael-128", NULL, "cbc", NULL);

int blocksize = mcrypt_enc_get_block_size(td);

if( buffer_len % blocksize != 0 ){return 1;}

mcrypt_generic_init(td, key, key_len, IV);

mcrypt_generic(td, buffer, buffer_len);

mcrypt_generic_deinit (td);

mcrypt_module_close(td);

return 0;

}

int decrypt(

void* buffer,

int buffer_len,

char* IV,

char* key,

int key_len

){

MCRYPT td = mcrypt_module_open("rijndael-128", NULL, "cbc", NULL);

int blocksize = mcrypt_enc_get_block_size(td);

if( buffer_len % blocksize != 0 ){return 1;}

mcrypt_generic_init(td, key, key_len, IV);

mdecrypt_generic(td, buffer, buffer_len);

mcrypt_generic_deinit (td);

mcrypt_module_close(td);

return 0;

}

void display(char* ciphertext, int len){

int v;

for (v=0; v<len; v++){

printf("%d ", ciphertext[v]);

}

printf("\n");

}

int main()

{

MCRYPT td, td2;

char * plaintext = "test text 123";

char* IV = "AAAAAAAAAAAAAAAA";

char *key = "0123456789abcdef";

int keysize = 16; /* 128 bits */

char* buffer;

int buffer_len = 16;

buffer = calloc(1, buffer_len);

strncpy(buffer, plaintext, buffer_len);

printf("==C==\n");

printf("plain: %s\n", plaintext);

encrypt(buffer, buffer_len, IV, key, keysize);

printf("cipher: "); display(buffer , buffer_len);

decrypt(buffer, buffer_len, IV, key, keysize);

printf("decrypt: %s\n", buffer);

return 0;

}