Abstract / Description of output
An important benchmark for secure multi-party computation (MPC) protocols is their round complexity. For several important MPC tasks, (tight) lower bounds on the round complexity are known. However, for some of these tasks, such as broadcast, the lower bounds can be circumvented when the termination round of every party is not a priori known, and simultaneous termination is not guaranteed. Protocols with this property are called probabilistic-termination (PT) protocols.
Running PT protocols in parallel affects the round complexity of the resulting protocol in somewhat unexpected ways. For instance, an execution of m protocols with constant expected
round complexity might take O(log m) rounds to complete. In a seminal work, Ben-Or and El-Yaniv (Distributed Computing ‘03) developed a technique for parallel execution of arbitrarily
many broadcast protocols, while preserving expected round complexity. More recently, Cohen et al. (CRYPTO ‘16) devised a framework for universal composition of PT protocols, and provided the first composable parallel-broadcast protocol with a simulation-based proof. These constructions crucially rely on the fact that broadcast is “privacy free,” and do not generalize to arbitrary protocols in a straightforward way. This raises the question of whether it is possible to execute arbitrary PT protocols in parallel, without increasing the round complexity.
In this paper we tackle this question and provide both feasibility and infeasibility results. We construct a round-preserving protocol compiler, secure against a minority of actively corrupted
parties, that compiles arbitrary protocols into a protocol realizing their parallel composition, while having a black-box access to the underlying protocols. Furthermore, we prove that the same
cannot be achieved, using known techniques, given only black-box access to the functionalities realized by the protocols, unless merely security against semi-honest corruptions is required, for
which case we provide a protocol.
Running PT protocols in parallel affects the round complexity of the resulting protocol in somewhat unexpected ways. For instance, an execution of m protocols with constant expected
round complexity might take O(log m) rounds to complete. In a seminal work, Ben-Or and El-Yaniv (Distributed Computing ‘03) developed a technique for parallel execution of arbitrarily
many broadcast protocols, while preserving expected round complexity. More recently, Cohen et al. (CRYPTO ‘16) devised a framework for universal composition of PT protocols, and provided the first composable parallel-broadcast protocol with a simulation-based proof. These constructions crucially rely on the fact that broadcast is “privacy free,” and do not generalize to arbitrary protocols in a straightforward way. This raises the question of whether it is possible to execute arbitrary PT protocols in parallel, without increasing the round complexity.
In this paper we tackle this question and provide both feasibility and infeasibility results. We construct a round-preserving protocol compiler, secure against a minority of actively corrupted
parties, that compiles arbitrary protocols into a protocol realizing their parallel composition, while having a black-box access to the underlying protocols. Furthermore, we prove that the same
cannot be achieved, using known techniques, given only black-box access to the functionalities realized by the protocols, unless merely security against semi-honest corruptions is required, for
which case we provide a protocol.
| Original language | English |
|---|---|
| Title of host publication | 44th International Colloquium on Automata, Languages, and Programming (ICALP 2017) |
| Publisher | Schloss Dagstuhl - Leibniz-Zentrum für Informatik |
| Pages | 37:1-37:15 |
| Number of pages | 15 |
| Volume | 80 |
| ISBN (Electronic) | 978-3-95977-041-5 |
| DOIs | |
| Publication status | Published - 14 Jul 2017 |
| Event | ICALP 2017: 44th International Colloquium on Automata, Languages, and Programming - Warsaw, Poland Duration: 10 Jul 2017 → 14 Jul 2017 http://icalp17.mimuw.edu.pl/ |
Publication series
| Name | Leibniz International Proceedings in Informatics (LIPIcs) |
|---|---|
| Publisher | Schloss Dagstuhl--Leibniz-Zentrum fuer Informatik |
| Volume | 80 |
| ISSN (Electronic) | 1868-8969 |
Conference
| Conference | ICALP 2017 |
|---|---|
| Abbreviated title | ICALP 2017 |
| Country/Territory | Poland |
| City | Warsaw |
| Period | 10/07/17 → 14/07/17 |
| Internet address |