RustCrypto: CMAC

Generic implementation of Cipher-based Message Authentication Code (CMAC), otherwise known as OMAC1.

Examples

We will use AES-128 block cipher from the aes crate.

To get the authentication code:

use aes::Aes128;
use cmac::{digest::KeyInit, Cmac, Mac};

// Create `Mac` trait implementation, namely CMAC-AES128
let mut mac = Cmac::<Aes128>::new_from_slice(b"very secret key.").unwrap();
mac.update(b"input message");

// `result` has type `Output` which is a thin wrapper around array of
// bytes for providing constant time equality check
let result = mac.finalize();
// To get underlying array use the `into_bytes` method, but be careful,
// since incorrect use of the tag value may permit timing attacks which
// defeat the security provided by the `Output` wrapper
let tag_bytes = result.into_bytes();

To verify the message:

use aes::Aes128;
use cmac::{digest::KeyInit, Cmac, Mac};

let mut mac = Cmac::<Aes128>::new_from_slice(b"very secret key.").unwrap();

mac.update(b"input message");

# let tag_bytes = mac.clone().finalize().into_bytes();
// `verify` will return `Ok(())` if tag is correct, `Err(MacError)` otherwise
mac.verify(&tag_bytes).unwrap();

License

Licensed under either of:

• Apache License, Version 2.0
• MIT license

at your option.

Contribution

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.