// SecretKeyFactory skf = SecretKeyFactory.getInstance(sa.getJCEAlgorithmString(), sa.getJCEProviderName());
byte keybytes[] = "01234567890123456789".getBytes();
SecretKey sk = new SecretKeySpec(keybytes, sa.getJCEAlgorithmString());
sa.initSign(sk);
sa.update("sdjhfkjashkjf".getBytes());
byte signatureValue[] = sa.sign();
System.out.println(Base64.encode(signatureValue));
doc.appendChild(sa.getElement());