Oblivious Blind Rendezvous for Non-anonymous Users

Abstract

In this chapter, we present symmetric algorithms for the blind rendezvous problem between two non-anonymous users. In the setting, we fix Alg and ID as:

$$\begin{aligned} RS = < Alg\text {-}S, Time, Port, Non\text {-}Anon, Obli> \end{aligned}$$

(13.1)

where $Port \in \{Port-S, Port-AS\}$ and $Time \in \{Syn, Asyn\}$. It is easy to see that there are 4 different rendezvous settings when Alg is fixed as symmetric, ID is fixed as non-anonymous, and Label is fixed as oblivious. The most difficult part in designing symmetric algorithms is to break symmetry among the indistinguishable users, such that the users in the system can perform differently from each other. In this chapter, we assume each user has distinct identifiers (IDs) and this information can help break symmetry in the distributed system. In Sect. 13.1, we present a rendezvous algorithm for two synchronous users when they start the oblivious rendezvous algorithm at the same time. This algorithm is not that efficient compared with the blind rendezvous algorithm for two synchronous users where the users share the same labels of the external ports. We then present two distributed algorithms for asynchronous users in Sect. 13.2. The intuitive idea is to design hopping sequences based on the differences in the users’ IDs. The first algorithm (ID Hopping) utilizes the user’s ID directly while the other one (Multi-Step channel Hopping) uses the converted bits of the user’s ID, which is similar to the idea of designing local sequence based algorithms in Chap. 9. In order to show the efficiency of the proposed algorithms, we present the lower bounds for oblivious blind rendezvous when the users are non-anonymous in Sect. 13.3. Finally, we summarize the chapter in Sect. 13.4.