protected void validateAuthenticationInfo(Hashtable<String, Object> environment)
        throws AuthenticationException
    {
        // validate when using Simple auth both principal and credentials are set
        if(SIMPLE_AUTHENTICATION_MECHANISM_NAME.equals(environment.get(Context.SECURITY_AUTHENTICATION))) {

            // only validate credentials if we have a non-empty principal
            if( environment.get(Context.SECURITY_PRINCIPAL) != null &&
                StringUtils.hasText( String.valueOf( environment.get(Context.SECURITY_PRINCIPAL) ))) {

                Object credentials = environment.get(Context.SECURITY_CREDENTIALS);

                // from the FAQ, we need to check for empty credentials:
                // http://docs.oracle.com/javase/tutorial/jndi/ldap/faq.html
                if( credentials == null ||
                    (credentials instanceof byte[] && ((byte[])credentials).length <= 0) || // empty byte[]
                    (credentials instanceof char[] && ((char[])credentials).length <= 0) || // empty char[]
                    (String.class.isInstance(credentials) && !StringUtils.hasText(String.valueOf(credentials)))) {

                    throw new javax.naming.AuthenticationException("LDAP Simple authentication requires both a "
                                                                       + "principal and credentials.");
                }
            }
        }
    }

}

    }

    /**
     * Returns a hex-encoded string of the underlying {@link #getBytes byte array}.
     * <p/>
     * This implementation caches the resulting hex string so multiple calls to this method remain efficient.
     * However, calling {@link #setBytes setBytes} will null the cached value, forcing it to be recalculated the
     * next time this method is called.
     *
     * @return a hex-encoded string of the underlying {@link #getBytes byte array}.
     */
    public String toHex() {
        if (this.hexEncoded == null) {
            this.hexEncoded = Hex.encodeToString(getBytes());
        }
        return this.hexEncoded;
    }

    /**
     * Returns a Base64-encoded string of the underlying {@link #getBytes byte array}.
     * <p/>
     * This implementation caches the resulting Base64 string so multiple calls to this method remain efficient.
     * However, calling {@link #setBytes setBytes} will null the cached value, forcing it to be recalculated the
     * next time this method is called.
     *
     * @return a Base64-encoded string of the underlying {@link #getBytes byte array}.
     */
    public String toBase64() {
        if (this.base64Encoded == null) {
            //cache result in case this method is called multiple times.
            this.base64Encoded = Base64.encodeToString(getBytes());
        }
        return this.base64Encoded;
    }

    /**
     * Simple implementation that merely returns {@link #toHex() toHex()}.
     *
     * @return the {@link #toHex() toHex()} value.
     */
    public String toString() {
        return toHex();
    }

    /**
     * Returns {@code true} if the specified object is a Hash and its {@link #getBytes byte array} is identical to
     * this Hash's byte array, {@code false} otherwise.
     *
     * @param o the object (Hash) to check for equality.
     * @return {@code true} if the specified object is a Hash and its {@link #getBytes byte array} is identical to
     *         this Hash's byte array, {@code false} otherwise.
     */
    public boolean equals(Object o) {
        if (o instanceof Hash) {
            Hash other = (Hash) o;
            return MessageDigest.isEqual(getBytes(), other.getBytes());
        }
        return false;
    }

    /**
     * Simply returns toHex().hashCode();
     *
     * @return toHex().hashCode()
     */
    public int hashCode() {
        if (this.bytes == null || this.bytes.length == 0) {
            return 0;
        }
        return Arrays.hashCode(this.bytes);
    }

        return hash(bytes, salt, DEFAULT_ITERATIONS);
    }

    /**
     * Hashes the specified byte array using the given {@code salt} for the specified number of iterations.
     *
     * @param bytes          the bytes to hash
     * @param salt           the salt to use for the initial hash
     * @param hashIterations the number of times the the {@code bytes} will be hashed (for attack resiliency).
     * @return the hashed bytes.
     * @throws UnknownAlgorithmException if the {@link #getAlgorithmName() algorithmName} is not available.
     */
    protected byte[] hash(byte[] bytes, byte[] salt, int hashIterations) throws UnknownAlgorithmException {
        MessageDigest digest = getDigest(getAlgorithmName());
        if (salt != null) {
            digest.reset();
            digest.update(salt);
        }
        byte[] hashed = digest.digest(bytes);
        int iterations = hashIterations - 1; //already hashed once above
        //iterate remaining number:
        for (int i = 0; i < iterations; i++) {
            digest.reset();
            hashed = digest.digest(hashed);
        }
        return hashed;
    }

    public boolean isEmpty() {