WS-Security is built on the XML-Signature and XML-Encryption standards, so, yes, you will need to understand at least parts of those. All those standards are listed in the Web Services FAQ, which is linked in my signature.
I have just finished a number of SCJWSD topics and now I am preparing myself to read about the web services securiry, anybody can help me how to start and what is the good tutorials and books that I can use to study it? is the xml security required to understand the ws security?