/**
     *
     */
    private static final int SIGNATURE_OFFSET = 48;
    private static final int SIGNATURE_LENGTH = 16;
    private final Mac digest;
    private final ReentrantLock signingLock = new ReentrantLock();
    private byte[] signingKey;
    private final String algorithmName;
    private final java.security.Provider provider;
    private volatile boolean closed = false;

    /**