In http://www.livejournal.com/support/faqbrowse.bml?faqid=149 (Where can I get an RSS or Atom feed of my journal? What is FOAF?), there's a mention of digest authentication for reading restricted entries in RSS feeds, but there's no indication of which algorithms are supported (of the ones listed in http://www.iana.org/assignments/http-dig-alg). I assume that MD5 is and UNIX(ck)?sum aren't, but what about SHA1?
I'm not sure where that tidbit would go (probably not in FAQ 149 itself, or in any FAQ. Perhaps howto with a link in FAQ 149 further reading?), but I'm willing to take a swing at it, or would be if I had the info.