Section 2.9. Summary of Encryption


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. Those cryptosystems allowed us to introduce the two basic methods of enciphermentsubstitution and transposition or permutationas 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 Chapter 12.

Finally, we introduced several very important and widely used applications of cryptography: hash functions, key exchange protocols, digital signatures, and certificates. Key exchange, especially with public key cryptography, is used by almost everyone. For example, any time a user enters "secure" (HTTPS) mode on a browser, a key exchange protocol is involved. Digital signatures give us a reliable means to prove the origin of data or code. To support digital signatures, cryptographic hash codes offer a fast, fairly reliable way of determining whether a piece of data has been modified between sender and receiver. Finally, certificates and their distribution allow us to trust information from someone or someplace else, even if we do not have direct interaction.

With these toolssymmetric encryption, public key encryption, key exchange protocols, digital signatures, cryptographic hash codes, and certificateswe are ready to study how threats in major application areas (such as program code, operating systems, database management systems, and networks) can be countered with controls, some of which depend on cryptography. You will see references to cryptography throughout the rest of this book, for example, signed code to show its origin in Chapter 7, cryptographic sealing of sensitive data in databases in Chapter 6, SSL encryption for browsers in Chapter 7, encryption for privacy in data mining in Chapter 10, and cryptographically secured e-mail in Chapter 7. Although cryptography is not the only control for the computer security specialist, it is certainly a very important one.

In the next chapter we look at another major way we achieve security: programs. Throughout a computer, code both permits and controls our computer activity. In Chapter 3 we begin by studying applications and work our way through operating systems and databases to networks in Chapter 7.




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

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