code: public byte[] sign(byte[] headerBytes, byte[] payloadBytes) throws SignatureGenerationException {
      	// default implementation; keep around until sign(byte[]) method is removed
      	byte[] contentBytes = new byte[headerBytes.length + 1 + payloadBytes.length];
      	
      	System.arraycopy(headerBytes, 0, contentBytes, 0, headerBytes.length);
      	contentBytes[headerBytes.length] = (byte)'.';
      	System.arraycopy(payloadBytes, 0, contentBytes, headerBytes.length + 1, payloadBytes.length);
      	
      	return sign(contentBytes);
      }
docs: Sign the given content using this Algorithm instance.
  
  @param headerBytes an array of bytes representing the base64 encoded header content to be verified against the signature.
  @param payloadBytes an array of bytes representing the base64 encoded payload content to be verified against the signature.
  @return the signature in a base64 encoded array of bytes
  @throws SignatureGenerationException if the Key is invalid.