Module crypto::hmac

HMAC (RFC 2104) over any hash.

Hmac<H> is the HMAC construction written once over hash.h's BlockHash, so HMAC-SHA1 / -SHA224 / -SHA256 / -SHA384 / -SHA512 are the same code with a different hash context. It streams like a hash, and is a Hasher itself (update / finish / digest_size): hash_bytes and any generic<H: Hasher> code take it.

struct Hmac<Sha512Ctx> mac = Hmac::new(Sha512Ctx::new(), key, keyLen);
mac.update(msg, msgLen);
mac.finish(&tag[0]);                       // 64 bytes: mac.digest_size()

hmac_sha256 is the one-shot form for HMAC-SHA256.