} finally {
            this.signingLock.unlock();
        }
    }

    /**
     * Securely wipe signing key from memory
     */
    public void secureWipeKey() {
        this.signingLock.lock();
        try {
            if (this.signingKey != null) {
                java.util.Arrays.fill(this.signingKey, (byte) 0);
                this.signingKey = null;

            CommonServerMessageBlock response = mock(CommonServerMessageBlock.class);

            digest.sign(data, 0, data.length, request, response);

            // Wipe the key
            digest.secureWipeKey();

            // Verify digest fails after wiping
            byte[] newData = new byte[128];
            Arrays.fill(newData, (byte) 0x66);

            assertThrows(IllegalStateException.class, () -> {