PHP sodium_crypto_kdf_keygen() Function: Usage and Examples

sodium_crypto_kdf_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_kdf_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_kdf_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: Use a unique non-secret context and distinct identifiers for domains; protect the master key.

Example 1: Basic Operation

Context strings must be exactly eight bytes; use distinct subkey IDs for independent uses.

<?php
$key = sodium_crypto_kdf_keygen();
echo strlen($key) === SODIUM_CRYPTO_KDF_KEYBYTES ? "correct size" : "wrong size";

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_kdf_keygen();
$second = sodium_crypto_kdf_keygen();
var_dump(!hash_equals($key, $second));
echo strlen($key) === SODIUM_CRYPTO_KDF_KEYBYTES ? "correct size" : "wrong size";

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_kdf_keygen();
$second = sodium_crypto_kdf_keygen();
var_dump(strlen($second) === strlen($key) && !hash_equals($key, $second));
echo strlen($key) === SODIUM_CRYPTO_KDF_KEYBYTES ? "correct size" : "wrong size";

Important Behavior and Edge Cases

Use a unique non-secret context and distinct identifiers for domains; protect the master key.

Use a unique non-secret context and distinct identifiers for domains; protect the master key.

Comparison with Related Functions

Common Beginner Mistakes

Key Takeaways

• sodium_crypto_kdf_keygen generates a securely random secret key with the exact size required by its matching primitive.
• Use a unique non-secret context and distinct identifiers for domains; protect the master key.
• sodium_crypto_pwhash derives a key from a human password instead of a strong master key.

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