poly1305

Poly1305 is a one-time authenticator originally designed by D. J. Bernstein. Poly1305 takes a 32-byte one-time key and a message and produces a 16-byte tag. It can be used to verify the data integrity and the authenticity of a message.

This module provide poly1305 message authentication code (MAC) for V Language. As a note, a key must only be used for a single message . Authenticating two different messages with the same key allows an attacker to forge authenticators for other messages with the same key.

Installation

You can install this module from github.

v install https://github.com/blackshirt/poly1305

Usage

1. Provide your secret keys with length 32 bytes, you can generate its randomly from crypto.rand or you can use chacha20.otk_key_gen() for generating one-time key intended for poly1305 keygen. If you want to use chacha20.otk_key_gen() function, you should install chacha20 module to your path. Its available at chacha20

2. If you would use chacha20.otk_key_gen provide its with nonce bytes, with length 12 or 24 bytes.

3. And then generates one-time key with chacha20.otk_key_gen .

4. Create Poly1305 mac instance with generated one-time key. If you are not going to use chacha20.otk_key_gen to generate key, make sure your key random enought to create poly1305 (feeds it with crypto.rand )

5. feeds your poly1305 instance with messages you want to be authenticated by calling write method.

6. And then, call finalize to produce your 16 byte tag associated with your messages.

module main 

import crypto.rand 

import blackshirt.chacha20
import blackshirt.poly1305

fn main() {
    // messages to auth
    msg := 'Hello my Girls.....!!'.bytes()

    // provides key with length 32 bytes
    key := rand.read(32) ?
    
    // provides your nonce with length 12 or 24 bytes
    nonce := rand.read(12) ?
    
    // and then create one-time key for poly1305
    otk := chacha20.otk_key_gen(key, nonce)

    // create new poly305 mac
    mut poly := poly1305.new_with_key(otk) ?

    // or if you dont want using `chacha20.otk_key_gen`, you can directly 
    // using key to instantiate poly1305 mac
    // mut poly := poly1305.new_with_key(key) ?

    // write message to mac
    poly.write(msg)

    // and then call finalize to produce 16 byte tag
    tag := poly.finalize()

    res := poly1305.verify_mac(tag, msg, otk) ?
    if res {
        println('Verified')
    } else {
        println('Not verified')
    }
}

License

MIT