Responsive Round Complexity and Concurrent Zero-Knowledge

The number of communication rounds is a classic complexity measure for protocols; reducing round complexity is a major goal in protocol design. However, when the communication time is inconstant, and in particular, when one of the parties intentionally delays its messages, the round complexity measure may become meaningless. For example, if one of the rounds takes longer than the rest of the protocol, then it does not matter if the round complexity is bounded by a constant or by a polynomial. In this paper, we propose a complexity measure called responsive round complexity. Loosely speaking, a protocol has responsive round complexity m with respect to Party A, if it makes the following guarantee. If A’s longest delay in responding to a message in a run of the protocol is t, then, in that run, the overall communication time is at most m · t. The logic behind this definition is that if a party responds quickly to a message, whether it has a good connection or it just chooses not to d...

• Type: Conference
• Year: 2001
• Where: ASIACRYPT
• Authors: Tzafrir Cohen, Joe Kilian, Erez Petrank
• Keywords: ASIACRYPT 2001, Classic Complexity Measure, Complexity Measure, Cryptology, Responsive