This is an EXPERIMENTAL crypto library written for Arduino-like boards. It has never been seriously tested, let alone audited, nor has it been optimized for performance. The code works, but is very slow and likely contains several side-channels. You are hereby STRONGLY discouraged from using it for anything but experimentation. You have been warned.
The library provides two classes called Cipher and HMAC, which can be used for encryption, decryption, and authentication of data. These classes use the Twofish and SHA256 algorithms, respectively, to do their work. The Cipher class implements the CBC and CTR modes, which means it allows Twofish to be used as a block cipher or as a stream cipher. The only supported key size is 256 bits.
The library has been tested to work on Arduino Uno R3, Intel Galileo Gen2, and Texas Instruments CC3200 boards.
Note: For brevity's sake, error checking, key generation, etc. is omitted
uint8_t key[32], iv[16];
uint8_t plaintext_a[128];
uint8_t plaintext_b[128];
uint8_t ciphertext[128];
int32_t clen, plen;
Cipher ciph;
/* Need to generate key, IV here */
ciph.init(key, sizeof(key));
ciph.setMode(CIPHER_MODE_CBC);
ciph.setIV(iv, sizeof(iv));
clen = ciph.encrypt(plaintext_a, sizeof(plaintext_a), ciphertext, sizeof(ciphertext));
ciph.setIV(iv, sizeof(iv));
plen = ciph.decrypt(ciphertext, clen, plaintext_b, sizeof(plaintext_b));
uint8_t key[32];
uint32_t ctr;
uint8_t plaintext_a[128];
uint8_t plaintext_b[128];
uint8_t ciphertext[128];
int32_t clen, plen;
Cipher ciph;
/* need to generate key here, and set `ctr' */
ciph.init(key, sizeof(key));
ciph.setMode(CIPHER_MODE_CTR);
ciph.setCounter(ctr);
clen = ciph.encrypt(plaintext_a, sizeof(plaintext_a), ciphertext, sizeof(ciphertext));
ciph.setCounter(ctr);
plen = ciph.decrypt(ciphertext, clen, plaintext_b, sizeof(plaintext_b));
uint8_t key[32];
uint8_t data[128];
uint8_t hash[HMAC_OUTPUT_SIZE];
HMAC hmac;
/* Need to generate key here */
hmac.init(key, sizeof(key));
hmac.authenticate(data, sizeof(data), hash, sizeof(hash));
if(hmac.verify(data, sizeof(data), hash, sizeof(hash)) < 0) {
/* Verification failed */
} else {
/* HMAC looks good */
}