folding in nick's suggestion

   information into the hostname will be too long for a typical hostname,

   we instead use a layer of indirection. We encode a hash of Bob's PK

   (10 bytes is sufficient since we're not worrying about collisions),

   and also the authentication token (empty for now). Thus at a bit more

   than 6 bits encoded per character (assuming only alphanumeric and

   hyphen), we transform the hostname "moria.mit.edu" into the hostname

   "moria.mit.edu.onion5gfmjsda-ckd5" (adding 13 characters plus the

   separator).

   [I thought we were going to do something more like "56fmjsda-ckd5.onion",

   leaving off moria.mit.edu.  This would have the advantage of not confusing

   users if the domain name part ('moria.mit.edu') doesn't match the key.

   Also, having a separate onion 'virtual TLD' is kinda more in the spirit

   of DNS as it stands. -NM]

   and also the authentication token (empty for now). Location-hidden

   services use the special top level domain called '.onion': thus

   hostnames take the form x.y.onion where x is the hash of PK, and y

   is the authentication cookie. If no cookie is required, the hostname

   can simply be of the form x.onion. Assuming only case insensitive

   alphanumeric and hyphen, we get a bit more than 6 bits encoded

   per character, meaning the x part of the hostname will be about

   13 characters.

   Alice's onion proxy examines hostnames and recognizes when they're

   destined for a hidden server. If so, it decodes the PK, looks it up in