.NET Security and Cryptography

Key Exchange Issues

One problem with symmetric cryptographic schemes is that distinct keys must be stored on each machine for each communicating pair to enable the sending and receiving of encrypted data. This means that the number of keys that need to be maintained as secrets by all communicating parties grows rapidly as the number of parties increases. If you have N parties, then the maximum number of keys that are potentially needed is the sum of the numbers from 1 to N – 1. Figure 3-12 shows how these keys start to proliferate for N = 1 and N = 4. Note that the number of required keys grows faster than the number of communicating parties. We will see how to solve this problem efficiently in the next chapter, using asymmetric algorithms to ...