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Chapter five deals with the advanced encryption standard Rijndael which is an encryption system based on symmetric key standards meant to replace DES which has recently been deemed as too insecure for commercial use. Rijndael was one of many finalists basically elicited due to a competition. Thus, the algorithm is perhaps not perfect and, as the book mentions, the other four finalists may be used in future crypto-systems. Rinndael, aside from having difficult computation, is based on the application of rounds, 10 for a 128 byte, otherwise 12 or 14 for other variations. The application was somewhat difficult to understand because it involves basically four different encryptions: the three transformations and then an XOR operation.

The significant part of this reading is mainly that this is a departure from the public key cryptosystems and indicates that despite the effectiveness of RSA and el gamal systems, symmetric key cryptosystems are still more efficient and cost effective than the public key counterparts. Rijndael is a block-cipher, indicating that this is still the preferred method of encryption for symmetric systems and, hopefully will be improved upon to make a truly secure symmetric system other than a one time pad.