Oblivious Blind Rendezvous for Anonymous Users

Abstract

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

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

(15.1)

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 anonymous, and Label is fixed as oblivious. Different from Chaps. 13 and 14, we assume the users have no distinct identifiers to break symmetry in distributed computing. This anonymous setting makes the oblivious blind rendezvous problem difficult. In Sect. 15.1, we show the hardness due to such anonymity which gives rise to the result that no deterministic algorithm could exist for the oblivious blind rendezvous problem. Then, we present in Sect. 15.2 an efficient randomized algorithm for two port-symmetric users no matter whether they are synchronous or asynchronous, which achieves short expected time to rendezvous. For the most difficult setting, where the users are port-asymmetric, we present randomized algorithms that work well for both synchronous and asynchronous users. Finally, we summarize the chapter in Sect. 15.4.