ParagonIE\Halite\KeyFactory::deriveEncryptionKeyPair PHP Method

    public static function deriveEncryptionKeyPair(HiddenString $password, string $salt, string $level = self::INTERACTIVE) : EncryptionKeyPair
    {
        $kdfLimits = self::getSecurityLevels($level);
        // VERSION 2+ (argon2)
        if (Util::safeStrlen($salt) !== \Sodium\CRYPTO_PWHASH_SALTBYTES) {
            throw new CryptoException\InvalidSalt('Expected ' . \Sodium\CRYPTO_PWHASH_SALTBYTES . ' bytes, got ' . Util::safeStrlen($salt));
        }
        // Diffie Hellman key exchange key pair
        $seed = \Sodium\crypto_pwhash(\Sodium\CRYPTO_BOX_SEEDBYTES, $password->getString(), $salt, $kdfLimits[0], $kdfLimits[1]);
        $keyPair = \Sodium\crypto_box_seed_keypair($seed);
        $secretKey = \Sodium\crypto_box_secretkey($keyPair);
        // Let's wipe our $kp variable
        \Sodium\memzero($keyPair);
        return new EncryptionKeyPair(new EncryptionSecretKey(new HiddenString($secretKey)));
    }

 public function testLegacyEncKeyStorage()
 {
     $enc_keypair = KeyFactory::deriveEncryptionKeyPair('apple', "
\t\n\v\f\r" . "", true);
     $enc_secret = $enc_keypair->getSecretKey();
     $enc_public = $enc_keypair->getPublicKey();
     $file_secret = \tempnam(__DIR__ . '/tmp', 'key');
     $file_public = \tempnam(__DIR__ . '/tmp', 'key');
     $this->assertTrue(KeyFactory::save($enc_secret, $file_secret) !== false);
     $this->assertTrue(KeyFactory::save($enc_public, $file_public) !== false);
     $load_public = KeyFactory::loadEncryptionPublicKey($file_public);
     $this->assertTrue($load_public instanceof EncryptionPublicKey);
     $this->assertTrue(\hash_equals($enc_public->getRawKeyMaterial(), $load_public->getRawKeyMaterial()));
     \unlink($file_secret);
     \unlink($file_public);
 }