Is there any way to compute AES CMAC with OpenSSL
/libcrypto
?
Preferably in a way that takes advantage of AES-NI (or any other hardware acceleration).
See also CMAC Key generation with OpenSSL EVP_DigestSign* fails
As stated in my blog post you can use the CMAC_CTX_new
, CMAC_Init
, CMAC_Update
and CMAC_Final
from lib crypto
to calculate AES-128-CBC CMAC. Here is an example:
#include <stdio.h>
#include <openssl/cmac.h>
void printBytes(unsigned char *buf, size_t len) {
for(int i=0; i<len; i++) {
printf("%02x ", buf[i]);
}
printf("\n");
}
int main(int argc, char *argv[])
{
// https://tools.ietf.org/html/rfc4493
// K, M and T from
// http://csrc.nist.gov/publications/nistpubs/800-38B/Updated_CMAC_Examples.pdf
// D.1 AES-128
// K: 2b7e1516 28aed2a6 abf71588 09cf4f3c
unsigned char key[] = { 0x2b,0x7e,0x15,0x16,
0x28,0xae,0xd2,0xa6,
0xab,0xf7,0x15,0x88,
0x09,0xcf,0x4f,0x3c};
// M: 6bc1bee2 2e409f96 e93d7e11 7393172a Mlen: 128
unsigned char message[] = { 0x6b,0xc1,0xbe,0xe2,
0x2e,0x40,0x9f,0x96,
0xe9,0x3d,0x7e,0x11,
0x73,0x93,0x17,0x2a };
unsigned char mact[16] = {0};
size_t mactlen;
CMAC_CTX *ctx = CMAC_CTX_new();
CMAC_Init(ctx, key, 16, EVP_aes_128_cbc(), NULL);
printf("message length = %lu bytes (%lu bits)\n",sizeof(message), sizeof(message)*8);
CMAC_Update(ctx, message, sizeof(message));
CMAC_Final(ctx, mact, &mactlen);
printBytes(mact, mactlen);
/* expected result T = 070a16b4 6b4d4144 f79bdd9d d04a287c */
CMAC_CTX_free(ctx);
return 0;
}