DES

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Data Encryption Standard (DES) is a cipher selected as an official Federal Information Processing Standard (FIPS) for the United States in 1976. The algorithm was initially controversial, with classified design elements, a relatively short key length, and suspicions about a National Security Agency (NSA) backdoor. DES consequently came under intense academic scrutiny, and motivated the modern understanding of block ciphers and their cryptanalysis.

DES was the first government-approved standard for encrypting sensitive information and grew out of research by IBM Corp. and the secretive U.S. National Security Agency (NSA), according to Paul Kocher, president of Cryptography Research Inc [1]. The algorithm, sometimes referred to as "single DES" uses a 56-bit key to encrypt blocks of data, and can produce up to 72,000,000,000,000,000 unique keys.

Cryptanalysis

In 1998, the EFF (Electronic Frontier Fundation) built a dedicated machine in order to show to the world that DES is not a secure algorithm any longer given the technology available [2]. Deep Crack, the name of the machine, costs $200,000 and is built with 1536 dedicated chips. It was able to recover a key with the help of an exhaustive search in 4 days in average, checking 92 billions of keys each second.

If you don't have money to build such expensive machines, use technology to your advantage. Volunteers are ready to donate their machine's idle time and the Internet is sufficient to take advantage of this. In January 1999, Distributed.Net, an organization specialized in collecting and managing computer's idle time, broke a DES key in 23 hours! More than 100,000 computers had done a little part of the work; this allowed a rate of 250,000,000,000 keys being checked every second.

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