Copy both aes128.c and aes128.h into your project and include the header where needed.
The opaque aes128_t type is used to maintain contexts for both AES encryption / decryption and CMAC generation.
Contexts are initialized using
void aes128_init(aes128_t *ctx, const uint8_t *iv, const uint8_t *key);and
void aes128_init_cmac(aes128_t *ctx, const uint8_t *key);Initializing a context for encryption / decryption requires an Initialization Vector (IV) to be provided. This usually does not have to be kept secret, but it absolutely does need to be random.
Once initialized, data can be encrypted and decrypted in-place using
void aes128_encrypt(aes128_t *ctx, uint8_t *chunk, size_t length);and
void aes128_decrypt(aes128_t *ctx, uint8_t *chunk, size_t length);where chunk points to length (at least 16) bytes to be encrypted or decrypted using the provided aes128_t context.
Initialization of a CMAC context only requires a key to be provided. Once initialized, a tag can be computed using
void aes128_cmac(const aes128_t *ctx, const uint8_t *msg, size_t length, uint8_t *mac);where msg points to length bytes to be used, computing a tag at mac. Unlike with aes128_encrypt() and aes128_decrypt(), length does not have to be a minimum of 16-bytes.
See aes128.h for additional API reference