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Applied Cryptography: Protocols, Algorithms and Source Code in C, 20th Anniversary Edition by Bruce Schneier

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CHAPTER 12

Data Encryption Standard (DES)

12.1 BACKGROUND

The Data Encryption Standard (DES), known as the Data Encryption Algorithm (DEA) by ANSI and the DEA-1 by the ISO, has been a worldwide standard for 20 years. Although it is showing signs of old age, it has held up remarkably well against years of cryptanalysis and is still secure against all but possibly the most powerful of adversaries.

Development of the Standard

In the early 1970s, nonmilitary cryptographic research was haphazard. Almost no research papers were published in the field. Most people knew that the military used special coding equipment to communicate, but few understood the science of cryptography. The National Security Agency (NSA) had considerable knowledge, but they did not even publicly admit their own existence.

Buyers didn't know what they were buying. Several small companies made and sold cryptographic equipment, primarily to overseas governments. The equipment was all different and couldn't interoperate. No one really knew if any of it was secure; there was no independent body to certify the security. As one government report said [441]:

The intricacies of relating key variations and working principles to the real strength of the encryption/decryption equipment were, and are, virtually unknown to almost all buyers, and informed decisions as to the right type of online, off-line, key generation, etc., which will meet buyers' security needs, have been most difficult to make.

In 1972, the National ...

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