Function poly1305_mac 

pub fn poly1305_mac(key: &[u8; 32], data: &[u8]) -> [u8; 16]

Computes the Poly1305 message authentication code as specified in RFC 8439.

key must be 32 bytes (r || s).

Example

use crypto::poly1305::poly1305_mac;

let key = b"0123456789abcdef0123456789abcdef";
let tag = poly1305_mac(key, b"message");