1. Krebs, B.: The Washington Post, Forty Percent of Web Users Surf with Unsafe Browsers, July 1 (2008)
2. Tyson, J.: How Encryption works: Introduction to How Encryption works
3. Stallings, W.: Cryptography and Network Security: Principles and Practices, 3rd edn., p. 45. Pearson Education, Inc and Dorling Kindersley Publishing Inc., USA (2006)
4. Stallings, W.: Cryptography and Network Security: Principles and Practices, 3rd edn., pp. 32–33. Pearson Education, Inc., USA (2006)
5. Callas, J.: An Introduction to Cryptography (September 2006)