Hi,
There are two main mistakes in your code:
- The output of the MD5 is 16 bytes long but you are allocating 8
bytes only. This will cause memory corruption.
- AES-256 expects the key to be 32-bytes long but you want to use an
MD5 digest as a key which is only 16-bytes. You should use SHA-256
instead for this purpose.
I hope this will help.
Cheers,
--
Mounir IDRASSI
IDRIX
http://www.idrix.fr
himas wrote:
Hello, I wrote a source for encrypting and decrypting some text data
with aes_256_cbc:
---------- CODE ----------
void aes256cbc_encrypt(char *text, char *hkey)
{
int i, outlen;
unsigned char *outbuf = (unsigned char*)malloc(1024);
unsigned char *inbuf = (unsigned char*)text;
int inlen = strlen(text);
unsigned char *key = (unsigned char*)hkey;
//unsigned char key[] = "somevalue";
EVP_CIPHER_CTX ctx;
const EVP_CIPHER *cipher;
EVP_CIPHER_CTX_init(&ctx);
cipher = EVP_aes_256_cbc();
EVP_EncryptInit(&ctx, cipher, key, NULL);
EVP_EncryptUpdate(&ctx, outbuf, &outlen, inbuf, inlen);
EVP_EncryptFinal(&ctx, outbuf + outlen, &outlen);
for(i = 0; i < outlen; i++) printf("%02x", outbuf[i]);
EVP_CIPHER_CTX_cleanup(&ctx);
free(outbuf);
}
int aes256cbc_decrypt(char *ctext, char *hkey)
{
int i, outlen;
unsigned char *outbuf = (unsigned char*)malloc(1024);
unsigned char *inbuf = (unsigned char*)ctext;
int inlen = strlen(ctext);
unsigned char *key = (unsigned char*)hkey;
printf("cyphered text = %s\nhashed key = %s\n", ctext, hkey);
EVP_CIPHER_CTX ctx;
const EVP_CIPHER *cipher;
EVP_CIPHER_CTX_init(&ctx);
cipher = EVP_aes_256_cbc();
EVP_DecryptInit(&ctx, cipher, key, NULL);
EVP_DecryptUpdate(&ctx, outbuf, &outlen, inbuf, inlen);
EVP_DecryptFinal(&ctx, outbuf + outlen, &outlen);
printf("\n[*] decryption result\n");
//for(i = 0; i < outlen; i++) printf("%02x", outbuf[i]);
for(i = 0; i < 16; i++) printf("%02x", outbuf[i]);
printf("\n%s \n", outbuf);
EVP_CIPHER_CTX_cleanup(&ctx);
free(outbuf);
}
main ()
{
char *pass = "testtesttesttest";
char *text = "testtesttesttest";
char *ctext = "fdfb4ca253caf79c683b85787de8d094";
// generating MD5 hash
char *chash = (char*)malloc(8);
MD5_Hash(pass, chash);
//aes256cbc_crypt(text, chash);
aes256cbc_decrypt(ctext, chash);
}
---------- CODE ----------
My questions concerning decryption are:
1. why don't I get outlen value?
2. why don't I get plaintext value after decryption (must be
"testtesttesttest")
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