Security in Computing, Third Edition

2.9. Summary of Encryption

This chapter has examined the basic processes of encryption and cryptanalysis. We began by describing what might be called “toy cryptosystems” because they illustrate principles of encryption but are not suitable for real use. These cryptosystems allowed us to introduce the two basic methods of encipherment—substitution and transposition or permutation—as well as techniques of cryptanalysis.

Then, we examined three “real” cryptosystems: DES, AES, and RSA, two symmetric and one asymmetric, which are used daily in millions of applications. We presented the characteristics of these cryptosystems, focusing on where they come from and how they are used, but not necessarily how they work. We save the internal details for ...