Section 12.5. Summary of Encryption


12.5. Summary of Encryption

In this chapter we have continued the study of encryption begun in Chapter 2. This chapter has focused on the details of the cryptographic algorithms, as well as on their weaknesses. Cryptography is certainly a field that learns from its mistakes.

To be a cryptographer you need to understand many topics in mathematics: number theory, algebra, analysis, and probability, to name a few. Computational complexity, the source of NP-complete problems, has elements of both mathematics and computer science. All these fields have hard problems and open questions. But the good cryptographer cannot simply look to hard or unsolved problems as a basis for secure algorithms, because tomorrow someone could solve one of these hard problems or find a partial solution that undermines the expected difficulty of those algorithms.

We have studied the details of two symmetric algorithms: the older DES and the newer AES. The DES algorithm is still appropriate for protecting data of moderate sensitivity, such as e-mail messages or files of private data that nobody would expend a significant effort to break. But the structural flaw in DES is its rigidity: as processors became more powerful, there was no way to extend the work factor associated with breaking a 56-bit DES encryption. The AES is much more flexible, so we can expect it to evolve as the power of processors improves. Its 128-, 192-, and 256-bit key size should last quite well, and, as the inventors point out, the algorithm extends naturally beyond 256 bits.

We also studied the RSA asymmetric algorithm. It remains useful because it can use any key length; the only limitation is that longer key lengths require significantly more time to encrypt.

The concept of quantum cryptography has been around for decades, but implementing it is only now becoming feasible. It offers an entirely different approach to cryptography, from which any field profits on occasion.




Security in Computing
Security in Computing, 4th Edition
ISBN: 0132390779
EAN: 2147483647
Year: 2006
Pages: 171

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