auth

Documentation

Overview

Package auth authenticates a message m using a secret key k.

The Sum function, viewed as a function of the message for a uniform random key, is designed to meet the standard notion of unforgeability. This means that an attacker cannot find authenticators for any messages not authenticated by the sender, even if the attacker has adaptively influenced the messages authenticated by the sender. For a formal definition see, e.g., Section 2.4 of Bellare, Kilian, and Rogaway, "The security of the cipher block chaining message authentication code," Journal of Computer and System Sciences 61 (2000), 362–399; http://www-cse.ucsd.edu/~mihir/papers/cbc.html.

auth does not make any promises regarding "strong" unforgeability; perhaps one valid authenticator can be converted into another valid authenticator for the same message. NaCl also does not make any promises regarding "truncated unforgeability."

This package is interoperable with NaCl: https://nacl.cr.yp.to/auth.html.

Example

package main

import (
	"fmt"

	"github.com/kevinburke/nacl"
	"github.com/kevinburke/nacl/auth"
)

func main() {
	// Load your secret key from a safe place and reuse it across multiple
	// Sum/Verify calls. (Obviously don't use this example key for anything
	// real.) If you want to convert a passphrase to a key, use a suitable
	// package like bcrypt or scrypt.
	key, err := nacl.Load("6368616e676520746869732070617373776f726420746f206120736563726574")
	if err != nil {
		panic(err)
	}

	mac := auth.Sum([]byte("hello world"), key)
	fmt.Printf("%x\n", *mac)
	result := auth.Verify(mac, []byte("hello world"), key)
	fmt.Println(result)
}

Output:

eca5a521f3d77b63f567fb0cb6f5f2d200641bc8dada42f60c5f881260c30317
true

Index

• Constants
• func Sum(m []byte, key nacl.Key) *[Size]byte
• func Verify(digest *[Size]byte, m []byte, key nacl.Key) bool

Examples

• Package

Constants

const Size = 32

Size is the size, in bytes, of an authenticated digest.

Functions

func Sum

func Sum(m []byte, key nacl.Key) *[Size]byte

Sum generates an authenticator for m using a secret key and returns the 32-byte digest.

func Verify

func Verify(digest *[Size]byte, m []byte, key nacl.Key) bool

Verify checks that digest is a correct authenticator of a message m under the secret key key. If not, the function returns false. Verify does not leak timing information.