pub trait Key: Send + Sync {
    // Required methods
    fn sign_concat(&self, first: &[u8], middle: &[&[u8]], last: &[u8]) -> Tag;
    fn tag_len(&self) -> usize;
    // Provided method
    fn sign(&self, data: &[&[u8]]) -> Tag { ... }
}Expand description
A HMAC key that is ready for use.
The algorithm used is implicit in the Hmac object that produced the key.