EFF DES cracker

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File:Board300.jpg
The EFF's US$250,000 DES cracking machine contained over 1,800 custom chips and could brute force a DES key in a matter of days — the photo shows a DES Cracker circuit board fitted with several Deep Crack chips

In cryptography, the EFF DES cracker (nicknamed "Deep Crack") is a machine built by the Electronic Frontier Foundation (EFF) to perform a brute force search of DES cipher's keyspace—that is, to decrypt an encrypted message by trying every possible key. The aim in doing this was to prove that DES's key is not long enough to be secure.

Contents

Background

DES uses a 56-bit key, meaning that there are 256 possible keys under which a message can be encrypted. This is approximately 7.21Template:E (more than 72 quadrillion). When DES was approved as a federal standard in 1976, it was thought that a machine fast enough to test that many keys in a reasonable time would cost an unreasonable amount of money to build, or that a machine cheap enough to be reasonable could not test that many keys in a reasonable time.

The DES challenges

Since DES was a federal standard, the US government encouraged the use of DES for all non-classified data. Considering the EFF's success with Deep Crack, it is not unreasonable to suppose that the NSA had also built such a machine, given their considerable financial resources. RSA Security wished to demonstrate that DES's key length was not enough to ensure security, so they set up the DES Challenges in 1997, offering a money prize. The first DES Challenge was solved in 96 days by the DESCHALL Project led by Rocke Verser in Loveland, Colorado. RSA Security set up DES Challenge II-1, which was solved by distributed.net in 41 days in January and February of 1998.

In 1998 the EFF built Deep Crack. It cost less than $250,000 to build.<ref>DES Cracker Project</ref> In response to DES Challenge II-2, on July 17, 1998, Deep Crack decrypted a DES-encrypted message after only 56 hours of work, winning $10,000. This was the final blow to DES, against which there were already some published cryptanalytic attacks. The brute force attack showed that cracking DES was actually a very practical proposition. For well-endowed governments or corporations, building a machine like Deep Crack would be no problem.

Six months later, in response to RSA Security's DES Challenge III, in collaboration with distributed.net, the EFF used Deep Crack to decrypt another DES-encrypted message, winning another $10,000. This time, the operation took less than a day — 22 hours and 15 minutes. The decryption was completed on January 19, 1999. In October of that year, DES was reaffirmed as a federal standard, but this time the standard recommended Triple DES (also referred to as 3DES or TDES).

The small key-space of DES, and relatively high computational costs of triple DES resulted in its replacement by AES as a Federal standard, effective May 26, 2002.

Technology

The EFF's DES cracker "Deep Crack" custom microchip.

Deep Crack was designed by Cryptography Research, Inc.; Advanced Wireless Technologies and the EFF. The principal designer was Paul Kocher, president of Cryptography Research. Advanced Wireless Technologies built 1856 custom DES chips (called Deep Crack or AWT-4500), housed on 29 circuit boards of 64 chips each. The boards are then fitted in six cabinets. The search is coordinated by a single PC which assigns ranges of keys to the chips. The entire machine was capable of testing over 90 billion keys per second. It would take about 5 days to test every possible key at that rate.

References

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  • Electronic Frontier Foundation, 1998, Cracking DES - Secrets of Encryption Research, Wiretap Politics & Chip Design, Oreilly & Associates Inc, {{{location}}}

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External links