Transforms transforms = new Transforms(doc);
transforms.addTransform(Transforms.TRANSFORM_ENVELOPED_SIGNATURE);
transforms.addTransform(Transforms.TRANSFORM_C14N_WITH_COMMENTS);
sig.addDocument("", transforms, Constants.ALGO_ID_DIGEST_SHA1);
sig.addKeyInfo(signingCert);
sig.sign(privateKey);
X509Certificate cert = sig.getKeyInfo().getX509Certificate();
sig.checkSignatureValue(cert.getPublicKey());
ByteArrayOutputStream bos = new ByteArrayOutputStream();