http://twistedmatrix.com/documents/current/web/howto/web-in-60/http-auth.html

twisted_web_http_digest_md5_sess.py

from zope.interface import implements

from twisted.cred.portal import IRealm, Portal
from twisted.cred.checkers import InMemoryUsernamePasswordDatabaseDontUse
from twisted.web.static import File
from twisted.web.resource import IResource
from twisted.web.guard import HTTPAuthSessionWrapper, DigestCredentialFactory
from twisted.web.server import Site
from twisted.internet import reactor

class PublicHTMLRealm(object):
    implements(IRealm)

    def requestAvatar(self, avatarId, mind, *interfaces):
        if IResource in interfaces:
            return (IResource, File("/tmp"), lambda: None)
        raise NotImplementedError()

portal = Portal(
    PublicHTMLRealm(),
    [InMemoryUsernamePasswordDatabaseDontUse(user='pass')],
    )

credentialFactory = DigestCredentialFactory("md5-sess", "localhost:8080")
resource = HTTPAuthSessionWrapper(portal, [credentialFactory])

factory = Site(resource)
print "Listening on 8080"
reactor.listenTCP(8080, factory)
reactor.run()