như vậy đã nếu bạn đã từng xem xét một bản đồ kết nối cho một mạng LAN hoặc WAN, mặc dù bạn có thể không có suy nghĩ về nó theo cách đó. Trong các bản đồ, các điểm đại diện cho máy tính cá nhân hoặc thiết bị định tuyến | Peer to Peer Harnessing the Power of Disruptive Technologies For example there are special batch verification methods for verifying many digital signatures at once that run much faster than checking each signature individually. 40 On the other hand sometimes these schemes leave themselves open to attack. 41 40 Mihir Bellare Juan A. Garay and Tal Rabin 1998 Fast Batch Verification for Modular Exponentiation and Digital Signatures EUROCRYPT 98 pp. 236-250. 41 Colin Boyd and Chris Pavlovski 2000 Attacking and Repairing Batch Verification Schemes ASIACRYPT 2000. The methods we ve described take advantage of particular properties of the problem at hand. Not all problems are known to have these properties. For example the SETI@home project would benefit from some quick method of checking correctness of its clients. This is because malicious clients have tried to disrupt the SETI@home project in the past. Unfortunately no quick practical methods for checking SETI@home computations are currently known. 42 42 David Molnar September 2000 The SETI@home Problem ACM Crossroads http crossroads columns onpatrol . Verifying bandwidth allocation can be a trickier issue. Bandwidth often goes hand-in-hand with data storage. For instance Bob might host a web page for Alice but is he always responding to requests A starting point for verification is to sample anonymously at random and gain some statistical assurance that Bob s server is up. Still the Mixmaster problem returns to haunt us. David Chaum who proposed mix nets in 1981 43 suggested that mix nodes publish the outgoing batch of messages. Alternatively they could publish some number per message selected at random by Alice and known only to her. This suggestion works well for a theoretical mix net endowed with a public bulletin board but in Internet systems it is difficult to ensure that the mix node actually sends out these messages. Even a bulletin board could be tampered with. 43 D. Chaum .
