src/PasswordLock.php
public static function upgradeFromVersion1(
        string $password,
        string $ciphertext,
        string $oldKey,
        Key $newKey
    ): string {
        if (!self::decryptAndVerifyLegacy($password, $ciphertext, $oldKey)) {
            throw new \Exception(
                'The correct password is necessary for legacy migration.'
            );
        }
        $plaintext = Crypto::legacyDecrypt($ciphertext, $oldKey);
        return self::hashAndEncrypt($plaintext, $newKey);
    }
public static function upgradeFromVersion1(
        string $password,
        string $ciphertext,
        string $oldKey,
        Key $newKey
    ): string {
        if (!self::decryptAndVerifyLegacy($password, $ciphertext, $oldKey)) {
            throw new \Exception(
                'The correct password is necessary for legacy migration.'
            );
        }
        $plaintext = Crypto::legacyDecrypt($ciphertext, $oldKey);
        return self::hashAndEncrypt($plaintext, $newKey);
    }
For migrating from an older version of the library

@param string $password
@param string $ciphertext
@param string $oldKey
@param Key $newKey
@return string
@throws \Exception