MessageDigest

private byte[] getDigestExtra(String toBeSigned, byte[] extra) throws NoSuchProviderException {
        MessageDigest md = null;
        try {
            md = MessageDigest.getInstance("SHA1", "BC");
            for (byte b : toBeSigned.getBytes()) {
                System.out.println("b: " + Hex.toHexString(new byte[]{b}));
                md.update(b);
            }
            for (byte b : extra) {
                System.out.println("b: " + Hex.toHexString(new byte[]{b}));
                md.update(b);
            }
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        }
        return md.digest();
    }
    
    private byte[] getDigest(String toBeSigned, byte[] extra) throws PGPException, IOException {
        JcaPGPDigestCalculatorProviderBuilder digestCalculatorProviderBuilder = new JcaPGPDigestCalculatorProviderBuilder();
        PGPDigestCalculator digestCalculator = digestCalculatorProviderBuilder.build().get(HashAlgorithmTags.SHA1);
        OutputStream os = digestCalculator.getOutputStream();

        for (byte b : toBeSigned.getBytes()) {
            os.write(b);
        }
        for (byte b : extra) {
            os.write(b);
        }
        return digestCalculator.getDigest();
    }