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Arduino Cryptography Library
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The library is split into four main sections: core, light-weight, legacy, and other.
Core algorithms are found within the "libraries/Crypto" directory in the repository:
Reduced memory versions of some algorithms (encryption is slower, but the RAM required for the key schedule is less):
The "tiny" versions only support encryption which makes them suitable for the CTR, CFB, OFB, EAX, and GCM block cipher modes but not CBC. The "small" versions use a little more memory but support both encryption and decryption.
The algorithms in the "libraries/CryptoLW" directory are new algorithms that have been designed for "light-weight" environments where memory and CPU resources are constrained:
These algorithms are fairly new, but they are ideal for Arduino devices. They don't appear in any internationally adopted standards yet but any algorithms that are adopted into standards later will be moved to the core library. Maybe you'll be the one to create that new standard!
Legacy algorithms in the "libraries/CryptoLegacy" directory are those that should probably not be used in new protocol designs, but may be required for backwards-compatibility with older protocols:
CBC is included in the legacy list because cryptography experts no longer recommend it for use in newer designs. It was an important mode in the past but newer designs should be using authenticated encryption with associated data (AEAD) instead. If you were looking to use CBC in your project, then please consider transitioning to one of the AEAD schemes listed above.
Over time, other algorithms may be moved from the core library to legacy.
Other algorithms are provided in the remaining directories under "libraries", and consist of algorithms that are either too big for the main library, or are dedicated to a special purpose that only some applications will need:
All cryptographic algorithms have been optimized for 8-bit Arduino platforms like the Uno. Memory usage is also reduced, particularly for SHA256 and SHA512 which save 192 and 512 bytes respectively over traditional implementations. For all algorithms, static sbox tables and the like are placed into program memory to further reduce data memory usage.
ChaCha with 20 rounds and 256-bit keys is the recommended symmetric encryption algorithm because it is twice as fast as AES128, constant-time, and much more secure. AES128, AES192, and AES256 are provided for use in applications where compatibility with other systems is desirable.
If code size is an issue for your application (for example on very low end Arduino variants), then Speck on AVR is less than half the code size of ChaCha, at the cost of more data memory for the state and longer key setup times. The SpeckTiny and SpeckSmall classes are even smaller at the cost of some performance when encrypting.
BLAKE2s and BLAKE2b are variations on the ChaCha stream cipher, designed for hashing, with 256-bit and 512-bit hash outputs respectively. They are intended as high performance replacements for SHA256 and SHA512 for when speed is critical but exact bit-compatibility of hash values is not. BLAKE2s and BLAKE2b support regular hashing, BLAKE2 keyed hashing, and HMAC modes.
All figures are for the Arduino Uno running at 16 MHz. Figures for the Ardunino Mega 2560 running at 16 MHz are similar:
| Encryption Algorithm | Encryption (per byte) | Decryption (per byte) | Key Setup | State Size (bytes) |
| AES128 (ECB mode) | 33.28us | 63.18us | 158.68us | 181 |
| AES192 (ECB mode) | 39.94us | 76.48us | 165.34us | 213 |
| AES256 (ECB mode) | 46.61us | 89.78us | 217.79us | 245 |
| AESTiny128 (ECB mode) | 40.37us | 10.16us | 18 | |
| AESTiny256 (ECB mode) | 56.84us | 17.20us | 34 | |
| AESSmall128 (ECB mode) | 40.37us | 71.36us | 134.22us | 34 |
| AESSmall256 (ECB mode) | 56.84us | 100.55us | 177.73us | 66 |
| ChaCha (20 rounds) | 14.87us | 14.88us | 43.74us | 132 |
| ChaCha (12 rounds) | 10.38us | 10.38us | 43.74us | 132 |
| ChaCha (8 rounds) | 8.13us | 8.14us | 43.74us | 132 |
| Speck (128-bit key, ECB mode) | 9.74us | 10.12us | 253.94us | 275 |
| Speck (192-bit key, ECB mode) | 10.03us | 10.41us | 264.63us | 275 |
| Speck (256-bit key, ECB mode) | 10.31us | 10.71us | 275.26us | 275 |
| SpeckSmall (128-bit key, ECB mode) | 33.93us | 34.82us | 207.66us | 67 |
| SpeckSmall (192-bit key, ECB mode) | 35.20us | 35.88us | 220.55us | 67 |
| SpeckSmall (256-bit key, ECB mode) | 36.46us | 36.93us | 233.32us | 67 |
| SpeckTiny (128-bit key, ECB mode) | 33.93us | 10.22us | 35 | |
| SpeckTiny (192-bit key, ECB mode) | 35.20us | 13.62us | 35 | |
| SpeckTiny (256-bit key, ECB mode) | 36.46us | 16.89us | 35 | |
| AEAD Algorithm | Encryption (per byte) | Decryption (per byte) | Key Setup | State Size (bytes) |
| ChaChaPoly | 41.20us | 41.19us | 902.36us | 221 |
| GCM<AES128> | 109.71us | 109.26us | 1265.69us | 284 |
| GCM<AES192> | 116.38us | 115.92us | 1485.56us | 316 |
| GCM<AES256> | 123.04us | 122.59us | 1760.28us | 348 |
| GCM<Speck> (256-bit key) | 86.74us | 86.29us | 646.88us | 378 |
| GCM<SpeckTiny> (256-bit key) | 112.90us | 112.44us | 1225.48us | 138 |
| EAX<AES128> | 71.14us | 71.14us | 1311.97us | 268 |
| EAX<AES256> | 97.80us | 97.80us | 1806.57us | 332 |
| EAX<Speck> (256-bit key) | 25.89us | 25.88us | 690.63us | 362 |
| EAX<SpeckTiny> (256-bit key) | 78.20us | 78.20us | 1269.19us | 122 |
| Acorn128 | 20.39us | 20.06us | 4817.82us | 60 |
| Ascon128 | 42.71us | 43.07us | 738.68us | 60 |
| Hash Algorithm | Hashing (per byte) | Finalization | State Size (bytes) | |
| SHA1 | 21.86us | 1421.86us | 95 | |
| SHA256 | 43.85us | 2841.04us | 107 | |
| SHA512 | 122.82us | 15953.42us | 211 | |
| SHA3_256 | 60.69us | 8180.24us | 205 | |
| SHA3_512 | 113.88us | 8196.34us | 205 | |
| BLAKE2s | 20.65us | 1335.25us | 107 | |
| BLAKE2b | 65.22us | 8375.34us | 211 | |
| Authentication Algorithm | Hashing (per byte) | Finalization | Key Setup | State Size (bytes) |
| SHA1 (HMAC mode) | 21.86us | 4290.62us | 1418.49us | 95 |
| SHA256 (HMAC mode) | 43.85us | 8552.61us | 2836.49us | 107 |
| BLAKE2s (Keyed mode) | 20.65us | 1335.25us | 1339.51us | 107 |
| BLAKE2s (HMAC mode) | 20.65us | 4055.56us | 1350.00us | 107 |
| BLAKE2b (Keyed mode) | 65.22us | 8375.34us | 8357.25us | 211 |
| Poly1305 | 26.26us | 489.11us | 17.06us | 53 |
| GHASH | 74.59us | 15.91us | 14.79us | 33 |
| XOF Algorithm | Hashing (per byte) | Extending (per byte) | Encryption (per byte) | State Size (bytes) |
| SHAKE128 | 49.43us | 49.02us | 49.59us | 206 |
| SHAKE256 | 60.77us | 60.37us | 60.93us | 206 |
| Public Key Operation | Time (per operation) | Comment | ||
| Curve25519::eval() | 2716ms | Raw curve evaluation | ||
| Curve25519::dh1() | 2718ms | First half of Diffie-Hellman key agreement | ||
| Curve25519::dh2() | 2717ms | Second half of Diffie-Hellman key agreement | ||
| Ed25519::sign() | 5148ms | Digital signature generation | ||
| Ed25519::verify() | 8196ms | Digital signature verification | ||
| Ed25519::derivePublicKey() | 5102ms | Derive a public key from a private key | ||
| P521::eval() | 46290ms | Raw curve evaluation | ||
| P521::dh1() | 46293ms | First half of Diffie-Hellman key agreement | ||
| P521::dh2() | 46304ms | Second half of Diffie-Hellman key agreement | ||
| P521::sign() | 60514ms | Digital signature generation | ||
| P521::verify() | 109078ms | Digital signature verification | ||
| P521::derivePublicKey() | 46290ms | Derive a public key from a private key | ||
| NewHope::keygen(), Ref | 639ms | Generate key pair for Alice, Ref version | ||
| NewHope::sharedb(), Ref | 1237ms | Generate shared secret and public key for Bob, Ref version | ||
| NewHope::shareda(), Ref | 496ms | Generate shared secret for Alice, Ref version | ||
| NewHope::keygen(), Torref | 777ms | Generate key pair for Alice, Torref version | ||
| NewHope::sharedb(), Torref | 1376ms | Generate shared secret and public key for Bob, Torref version | ||
| NewHope::shareda(), Torref | 496ms | Generate shared secret for Alice, Torref version | ||
Where a cipher supports more than one key size (such as ChaCha), the values are typically almost identical for 128-bit and 256-bit keys so only the maximum is shown above.
Due to the memory requirements, P521 and NewHope performance was measured on an Arduino Mega 2560 running at 16 MHz. They are too big to fit in the RAM size of the Uno.
All figures are for the Arduino Due running at 84 MHz:
| Encryption Algorithm | Encryption (per byte) | Decryption (per byte) | Key Setup | State Size (bytes) |
| AES128 (ECB mode) | 6.58us | 11.40us | 38.15us | 188 |
| AES192 (ECB mode) | 7.94us | 13.83us | 39.79us | 220 |
| AES256 (ECB mode) | 9.30us | 16.25us | 49.68us | 252 |
| AESTiny128 (ECB mode) | 7.23us | 1.25us | 20 | |
| AESTiny256 (ECB mode) | 10.62us | 1.43us | 36 | |
| AESSmall128 (ECB mode) | 7.23us | 12.33us | 23.44us | 36 |
| AESSmall256 (ECB mode) | 10.62us | 16.92us | 31.88us | 68 |
| ChaCha (20 rounds) | 0.87us | 0.88us | 4.96us | 136 |
| ChaCha (12 rounds) | 0.70us | 0.71us | 4.96us | 136 |
| ChaCha (8 rounds) | 0.62us | 0.62us | 4.96us | 136 |
| Speck (128-bit key, ECB mode) | 0.97us | 0.96us | 36.80us | 288 |
| Speck (192-bit key, ECB mode) | 1.00us | 0.98us | 38.14us | 288 |
| Speck (256-bit key, ECB mode) | 1.03us | 1.01us | 39.31us | 288 |
| SpeckSmall (128-bit key, ECB mode) | 2.72us | 2.30us | 26.89us | 80 |
| SpeckSmall (192-bit key, ECB mode) | 2.80us | 2.39us | 27.80us | 80 |
| SpeckSmall (256-bit key, ECB mode) | 2.90us | 2.48us | 29.08us | 80 |
| SpeckTiny (128-bit key, ECB mode) | 2.72us | 1.47us | 48 | |
| SpeckTiny (192-bit key, ECB mode) | 2.81us | 1.54us | 48 | |
| SpeckTiny (256-bit key, ECB mode) | 2.90us | 1.83us | 48 | |
| AEAD Algorithm | Encryption (per byte) | Decryption (per byte) | Key Setup | State Size (bytes) |
| ChaChaPoly | 1.71us | 1.71us | 45.08us | 240 |
| GCM<AES128> | 10.90us | 10.90us | 248.83us | 312 |
| GCM<AES192> | 12.30us | 12.31us | 296.83us | 344 |
| GCM<AES256> | 13.66us | 13.67us | 350.25us | 376 |
| GCM<Speck> (256-bit key) | 5.27us | 5.28us | 75.31us | 408 |
| GCM<SpeckTiny> (256-bit key) | 7.06us | 7.07us | 94.20us | 168 |
| EAX<AES128> | 12.33us | 12.33us | 234.91us | 280 |
| EAX<AES256> | 16.99us | 16.99us | 322.92us | 344 |
| EAX<Speck> (256-bit key) | 2.80us | 2.80us | 81.63us | 384 |
| EAX<SpeckTiny> (256-bit key) | 6.69us | 6.69us | 110.91us | 144 |
| Acorn128 | 0.75us | 0.75us | 175.70us | 64 |
| Ascon128 | 3.52us | 3.50us | 51.67us | 72 |
| Hash Algorithm | Hashing (per byte) | Finalization | State Size (bytes) | |
| SHA1 | 0.94us | 62.34us | 112 | |
| SHA256 | 1.15us | 76.60us | 120 | |
| SHA512 | 2.87us | 370.37us | 224 | |
| SHA3_256 | 5.64us | 735.29us | 224 | |
| SHA3_512 | 10.42us | 735.49us | 224 | |
| BLAKE2s | 0.80us | 53.39us | 120 | |
| BLAKE2b | 1.28us | 164.66us | 224 | |
| Authentication Algorithm | Hashing (per byte) | Finalization | Key Setup | State Size (bytes) |
| SHA1 (HMAC mode) | 0.94us | 196.74us | 68.06us | 112 |
| SHA256 (HMAC mode) | 1.15us | 238.98us | 80.44us | 120 |
| BLAKE2s (Keyed mode) | 0.80us | 53.39us | 55.10us | 120 |
| BLAKE2s (HMAC mode) | 0.80us | 168.20us | 57.60us | 120 |
| BLAKE2b (Keyed mode) | 1.28us | 164.66us | 166.68us | 224 |
| Poly1305 | 0.81us | 19.01us | 2.57us | 60 |
| GHASH | 4.47us | 1.52us | 2.60us | 36 |
| XOF Algorithm | Hashing (per byte) | Extending (per byte) | Encryption (per byte) | State Size (bytes) |
| SHAKE128 | 4.60us | 4.45us | 4.59us | 232 |
| SHAKE256 | 5.64us | 5.49us | 5.63us | 232 |
| Public Key Operation | Time (per operation) | Comment | ||
| Curve25519::eval() | 103ms | Raw curve evaluation | ||
| Curve25519::dh1() | 103ms | First half of Diffie-Hellman key agreement | ||
| Curve25519::dh2() | 104ms | Second half of Diffie-Hellman key agreement | ||
| Ed25519::sign() | 195ms | Digital signature generation | ||
| Ed25519::verify() | 306ms | Digital signature verification | ||
| Ed25519::derivePublicKey() | 194ms | Derive a public key from a private key | ||
| P521::eval() | 1503ms | Raw curve evaluation | ||
| P521::dh1() | 1503ms | First half of Diffie-Hellman key agreement | ||
| P521::dh2() | 1503ms | Second half of Diffie-Hellman key agreement | ||
| P521::sign() | 1860ms | Digital signature generation | ||
| P521::verify() | 3423ms | Digital signature verification | ||
| P521::derivePublicKey() | 1503ms | Derive a public key from a private key | ||
| NewHope::keygen(), Ref | 29ms | Generate key pair for Alice, Ref version | ||
| NewHope::sharedb(), Ref | 41ms | Generate shared secret and public key for Bob, Ref version | ||
| NewHope::shareda(), Ref | 9ms | Generate shared secret for Alice, Ref version | ||
| NewHope::keygen(), Torref | 42ms | Generate key pair for Alice, Torref version | ||
| NewHope::sharedb(), Torref | 53ms | Generate shared secret and public key for Bob, Torref version | ||
| NewHope::shareda(), Torref | 9ms | Generate shared secret for Alice, Torref version | ||
1.9.1