Generic implementation of Hash-based Message Authentication Code (HMAC).

To use it you'll need a cryptographic hash function implementation from RustCrypto project. You can either import specific crate (e.g. sha2), or meta-crate crypto-hashes which reexport all related crates.

Usage

Let us demonstrate how to use HMAC using SHA256 as an example.

To get the authentication code:

extern crate sha2;
extern crate hmac;

use hmac::{Hmac, Mac};
use sha2::Sha256;

// Create `Mac` trait implementation, namely HMAC-SHA256
let mac = Hmac::<Sha256>::new(b"my secret and secure key");
mac.input(b"my message");

// `result` has type `MacResult` which is a thin wrapper around array of
// bytes for providing constant time equality check
let result = mac.result();
// To get &[u8] use `code` method, but be carefull, since incorrect use
// of the code value may permit timing attacks which defeat the security
// provided by the `MacResult`.
let code_bytes = resul.code();

To verify the message:

let mac = Hmac::<Sha256>::new(b"my secret and secure key");

mac.input(b"input message");

let is_code_correct = mac.verify(code_bytes);