It is often argued that peer-to-peer systems can offer anonymity for

Question

(i) clients accessing resources

(ii) the hosts providing access to resources.

Discuss each of these propositions. Suggest a way in which the resistance to attacks on anonymity might be improved.

Answer 1

The general argument is that although TCP/IP messages contain the IP addresses of the source and destination nodes, when an application-level multi-hop routing overlay is used, only the previous and next node in the route can be discovered when packets are intercepted or logged somewhere in the network. A GUID does not by itself provide any information about the location of the node that hosts it. But if an attacker can gain knowledge of the contents of some of the routing tables, this property is compromised. Furthermore, an attacker with eavesdropping access at several points in the network could send ‘probe’ messages to specific GUIDs and observe the resulting IP traffic. This is likely to reveal quite a lot of information about the location of the GUID.
So the propositions that clients and resource hosts can remain anonymous is only true for weak attackers with limited access to the network.
This resistance to attacks might be improved by generating several outgoing messages for each incoming request at an intermediate node, all but one of the messages would be treated as a ‘dummy’ message and destroyed at the next node. This would incur a substantial additional cost in network traffic.