A pure-Rust, #![no_std], zero-allocation AES-CCM implementation ported
from [TinyCrypt] using [RustCrypto's AES].
CCM (for "Counter with CBC-MAC") mode is a NIST approved mode of operation defined in [SP 800-38C].
This implementation accepts: 1. Both non-empty payload and associated data (it encrypts and authenticates the payload and also authenticates the associated data). 2. Non-empty payload and empty associated data (it encrypts and authenticates the payload). 3. Non-empty associated data and empty payload (it degenerates to an authentication mode on the associated data).
The implementation accepts payloads of any length between 0 and 2^16 bytes and associated data of any length between 0 and (2^16 - 2^8) bytes.
```rust use aes_ccm::CcmMode;
let key = [ 0xC0, 0xC1, 0xC2, 0xC3, 0xC4, 0xC5, 0xC6, 0xC7, 0xC8, 0xC9, 0xCA, 0xCB, 0xCC, 0xCD, 0xCE, 0xCF, ]; let nonce = [ 0x00, 0x00, 0x00, 0x03, 0x02, 0x01, 0x00, 0xA0, 0xA1, 0xA2, 0xA3, 0xA4, 0xA5, ]; let ccm = CcmMode::new(&key, nonce, 8).unwrap();
let mut ciphertextbuf = [0u8; 50]; let payload = [ 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, ]; let associateddata = [0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07]; let ciphertext = ccm .generateencrypt(&mut ciphertextbuf, &associated_data, &payload) .unwrap();
let mut plaintextbuf = [0u8; 50]; let plaintext = ccm .decryptverify(&mut plaintextbuf, &associateddata, &ciphertext) .unwrap(); assert_eq!(&payload, plaintext); ```
I'm not a cryptographer and this hasn't been audited in any way. It is however a careful port of [TinyCrypt], so if it's sound, then this should be too.
The MAC length parameter is an important parameter to estimate the security against collision attacks (that aim at finding different messages that produce the same authentication tag). The implementation accepts any even integer between 4 and 16, as suggested in [SP 800-38C].
[RFC 3610], which also specifies CCM, presents a few relevant security suggestions, such as: * It is recommended that most applications use a MAC length greater than 8. * The usage of the same nonce for two different messages which are encrypted with the same key destroys the security of CCM mode.
Licensed under either of
at your option.
This is a port of TinyCrypt's CCM mode, its license file is in LICENSE-3RD-PARTY.
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.