DES Key Search Machine Design Information
The DES Key Search Machine uses a sieve-and-check search process that can find keys even when little is known about the plaintext. Each chip processes two separate ciphertexts and contains a 256-bit vector specifying which bytes can appear in the plaintext -- making it possible, for example, to find a key if the input message is simply known to consist of ASCII text.
As assembled, the machine is housed in six recycled SUN-2 cabinets and consists of 27 circuit boards that hold over 1800 custom chips. Each chip contains 24 search units, which independently scan through a range of keys, filtering out those that do not pass the search criteria for both of the ciphertexts. For example, search units may check the decrypted block to determine that it contains only ASCII text characters, or may verify that specific bytes match known or expected values. When a search unit finds a potential match, it stops until the the controlling computer (a PC running Windows 95 or Linux) retrieves the key and restarts that search unit. The PC tests keys against another more strict set of criteria to eliminate any incorrect keys that pass the search unit's tests. Over 37000 search units were active, testing more than 92 billion keys per second, when the RSA DES Challenge key was discovered on July 15, 1998.
Cost and development time were major factors the machine's design. Most of the expenses were one-time research and design costs. The total project budget remained under $250,000, making the machine the fastest, most economical key search device ever known to have been produced.
Designed by Cryptography Research, Advanced Wireless Technologies, and EFF, the record-breaking DES Key Search Machine won the RSA DES Challenge on July 15, 1998 after searching for 56 hours.
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Additional DES and DES Key Search Information
Pictures of the DES Key Search Machine.
New York Times. US Data-Scrambling Code Cracked With Homemade Equipment (site registration required).
DES specification (publication FIPS 46-2) and other information including a DES Fact Sheet from NIST.
Paper (text or postscript) by Matt Blaze et al. on DES key lengths and search feasibility.
Previous DES Challenge winners' info from distributed.net, Rocke Verser, or SolNET.
RSA Data Security.
Description of DESCHALL in the RSA Secret Key Challenge
Electronic Frontier Foundation.
About Cryptography Research.
About Paul Kocher.
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