We present a novel approach for protecting transactions over networks. While we use the example of a netbank application, the proposal is relevant for many security-critical transactions.

The approach is based on two major changes compared to current solutions. The first one is the use of individualized key derivation functions, which ensure that given the same input, each copy of the application ends up with different keys. The second contribution is the individualizing of program copies by subtle code modification. This makes automated analysis and patching of a client-side application very difficult. In combination, these techniques allow to build a secure channel between the client program and the server, while current solutions only build such a channel between the client computer and the server.