sodium_crypto_auth

(PHP 7 >= 7.2.0, PHP 8)

sodium_crypto_auth — Compute a tag for the message

Description

sodium_crypto_auth(string $message, #[\SensitiveParameter] string $key): string

Symmetric message authentication via sodium_crypto_auth() provides integrity, but not confidentiality.

Unlike with digital signatures (e.g. sodium_crypto_sign_detached()), any party capable of verifying a message is also capable of authenticating their own messages. (Hence, symmetric authentication.)

Parameters

message: The message you intend to authenticate
key: Authentication key

Return Values

Authentication tag

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User Contributed Notes

craig at craigfrancis dot co dot uk

6 years ago

Here's a quick example on how to use sodium_crypto_auth(); where you have a message that you want to sign, so anyone who can access the *shared* key can confirm that the message hasn't been tampered with.

This is similar to sodium_crypto_sign_detached(), but both signer and verifier have access to the same key.

<?php

$key = sodium_crypto_auth_keygen();

//--------------------------------------------------
// Person 1, signing

$message = 'Hello';

$signature = sodium_crypto_auth($message, $key);

//--------------------------------------------------
// Person 2, verifying

$message_valid = sodium_crypto_auth_verify($signature, $message, $key);

if (!$message_valid) {
    exit('Message has been changed.');
}

?>