PHP sodium_crypto_auth_keygen() Function: Usage and Examples

sodium_crypto_auth_keygen generates a securely random secret key with the exact size required by its matching primitive.

The examples explain the data format, expected results and the difference between this API and nearby cryptographic operations.

What It Does

The operation is intended for: sodium_crypto_auth_keygen generates a securely random secret key with the exact size required by its matching primitive.

The sodium extension must be enabled.

Syntax and Return Value

sodium_crypto_auth_keygen(): string

This API accepts no required parameters, or its signature must be checked on the target runtime.

The declared return type is shown above. Errors can include false results or exceptions depending on this API: Both parties must share the same secret. A MAC is not a public-key digital signature.

Example 1: Basic Operation

A keyed MAC authenticates a message; the tag is not encrypted data.

<?php
$key = sodium_crypto_auth_keygen();
echo strlen($key) === SODIUM_CRYPTO_AUTH_KEYBYTES ? "valid length" : "wrong length";

Example 2: A Different Use Case

Generate two independent keys and confirm the expected length and distinct random values.

<?php
// Check the alternative case.
$key = sodium_crypto_auth_keygen();
$second = sodium_crypto_auth_keygen();
var_dump(!hash_equals($key, $second));
echo strlen($key) === SODIUM_CRYPTO_AUTH_KEYBYTES ? "valid length" : "wrong length";

Practical Example: Checking the Result

Generate two independent keys and confirm the expected length and distinct random values.

<?php
// Verify the expected behavior before using results.
$key = sodium_crypto_auth_keygen();
$second = sodium_crypto_auth_keygen();
var_dump(strlen($second) === strlen($key) && !hash_equals($key, $second));
echo strlen($key) === SODIUM_CRYPTO_AUTH_KEYBYTES ? "valid length" : "wrong length";

Important Behavior and Edge Cases

Both parties must share the same secret. A MAC is not a public-key digital signature.

Both parties must share the same secret. A MAC is not a public-key digital signature.

Comparison with Related Functions

Common Beginner Mistakes

Key Takeaways

• sodium_crypto_auth_keygen generates a securely random secret key with the exact size required by its matching primitive.
• Both parties must share the same secret. A MAC is not a public-key digital signature.
• sodium_crypto_sign_detached instead uses public-key signatures.

Apply this behavior to a real application only after confirming the required extension, configuration and failure handling on the deployment runtime.