public void update(byte[] buf,int off,int len) throws SignatureException {
  if (RSAdata != null || digestAttr != null || isTsp)   messageDigest.update(buf,off,len);
 else   sig.update(buf,off,len);
}

public void update ( byte [ ] buf , int off , int len ) throws SignatureException { if ( RSAdata != null || digestAttr != null || isTsp ) messageDigest . update ( buf , off , len ) ; else sig . update ( buf , off , len ) ; }
update the digest with the specified bytes . this method is used both for signing and verifying
