what is the Rendezvous point identity ID

Question

I am currently reading the specification for rendezvous point and one little point has got me confused.

When constructing a packet to send to from Alice's OP to Introduction Point it asks for the Rendezvous point identity ID, I have not found this in any other of the Tor specification, could some one shed some light on what this is, is it simply the identity or identity hash of the Rendezvous point?

628         OR (in the v2 intro protocol)
 629           VER    Version byte: set to 2.        [1 octet]
 630           IP     Rendezvous point's address    [4 octets]
 631           PORT   Rendezvous point's OR port    [2 octets]
 632           ID     Rendezvous point identity ID [20 octets]
 633           KLEN   Length of onion key           [2 octets]
 634           KEY    Rendezvous point onion key [KLEN octets]

Also could anyone expand on what the identitier for Bob's PK is, I am using the v2 method. Is this the onion address I am trying to

617        Cleartext
 618           PK_ID  Identifier for Bob's PK      [20 octets]

Answer 1

The Rendezvous point identity ID is, as far as I can tell, just the Fingerprint of the Relay, being used as the Rendezvous point. These digests are hexed and use '$' as its prefix.

The ID of the Public Key is being explained in specification:

PK_ID is the hash of Bob's public key or the service key, depending on the hidden service descriptor version. In case of a v0 descriptor, Alice's OP uses Bob's public key. If Alice has downloaded a v2 descriptor, she uses the contained public key ("service-key").