40-bit encryption: Difference between revisions
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==Obsolescence== |
==Obsolescence== |
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All 40-bit and 56-bit encryption algorithms are [[obsolete]], because they are vulnerable to brute force attacks, and therefore cannot be regarded as secure{{ |
All 40-bit and 56-bit encryption algorithms are [[obsolete]], because they are vulnerable to brute force attacks, and therefore cannot be regarded as secure<ref>{{cite web|last1=University of California at Berkeley Public Information Office|title=The only legally exportable cryptography level is totally insecure; UC Berkeley grad student breaks challenge cipher in hours|url=http://www.berkeley.edu/news/media/releases/97legacy/code.html|publisher=The Regents of the University of California|accessdate=2015-12-14|date=1997-01-29|quote=This is the final proof of what we've known for years: 40-bit encryption technology is obsolete.}}</ref><ref>{{cite web|author1=Fitzmaurice, Ellen|author2=Tamaki, Kevin|title=Decoding the Encryption Debate: U.S. export restrictions and 'key recovery' policies are ineffectual as well as burdensome to business|url=http://articles.latimes.com/1997-06-01/local/me-64597_1_encryption-debate|website=Los Angeles Times|accessdate=2015-12-14|date=1997-06-01|quote=But recent advances in computing technology have rendered 40-bit encryption dangerously weak and export limits commercially obsolete.}}</ref>. As a result, virtually all Web browsers now use 128-bit keys, which are considered strong. Most [[Web server]]s will not communicate with a client unless it has 128-bit encryption capability installed on it. |
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Public/private key pairs used in [[asymmetric encryption]] (public key cryptography), at least those based on prime factorisation, must be much longer in order to be secure; see [[key size]] for more details. |
Public/private key pairs used in [[asymmetric encryption]] (public key cryptography), at least those based on prime factorisation, must be much longer in order to be secure; see [[key size]] for more details. |
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Revision as of 05:12, 14 December 2015
40-bit encryption refers to a key size of forty bits, or five bytes, for symmetric encryption; this represents a relatively low level of security. A forty bit length corresponds to a total of 240 possible keys. Although this is a large number in human terms (about a trillion, nearly two hundred times the world's human population), it is possible to break this degree of encryption using a moderate amount of computing power in a brute-force attack, i.e., trying out each possible key in turn.
Description
A typical home computer in 2004 could brute-force a 40-bit key in a little under two weeks, testing a million keys per second; modern computers are able to achieve this much faster. Using free time on a large corporate network or a botnet would reduce the time in proportion to the number of computers available.[1] With dedicated hardware, a 40-bit key can be broken in seconds. The Electronic Frontier Foundation's Deep Crack, built by a group of enthusiasts for US$250,000 in 1998, could break a 56-bit Data Encryption Standard (DES) key in days,[2] and would be able to break 40-bit DES encryption in about two seconds.[3]
40-bit encryption was common in software released before 1999, especially those based on the RC2 and RC4 algorithms,[citation needed] when algorithms with larger key lengths could not legally be exported from the United States without a case-by-case license. "In the early 1990s ... As a general policy, the State Department allowed exports of commercial encryption with 40-bit keys, although some software with DES could be exported to U.S.-controlled subsidiaries and financial institutions."[4][5] As a result, the "international" versions of web browsers were designed to have an effective key size of 40 bits when using Secure Sockets Layer to protect e-commerce. Similar limitations were imposed on other software packages, including early versions of Wired Equivalent Privacy. In 1992, IBM designed the CDMF algorithm to reduce the strength of 56-bit DES against brute force attack to 40 bits, in order to create exportable DES implementations.
Obsolescence
All 40-bit and 56-bit encryption algorithms are obsolete, because they are vulnerable to brute force attacks, and therefore cannot be regarded as secure[6][7]. As a result, virtually all Web browsers now use 128-bit keys, which are considered strong. Most Web servers will not communicate with a client unless it has 128-bit encryption capability installed on it.
Public/private key pairs used in asymmetric encryption (public key cryptography), at least those based on prime factorisation, must be much longer in order to be secure; see key size for more details.
As a general rule, modern symmetric encryption algorithms such as AES use key lengths of 128, 192 and 256 bits.
See also
Footnotes
- ^ Schneier 1996, p. 154.
- ^ EFF-1998.
- ^ Schneier 1996, p. 153.
- ^ Grimmett 2001.
- ^ Schneier 1996, p. 615.
- ^ University of California at Berkeley Public Information Office (January 29, 1997). "The only legally exportable cryptography level is totally insecure; UC Berkeley grad student breaks challenge cipher in hours". The Regents of the University of California. Retrieved December 14, 2015.
This is the final proof of what we've known for years: 40-bit encryption technology is obsolete.
- ^ Fitzmaurice, Ellen; Tamaki, Kevin (June 1, 1997). "Decoding the Encryption Debate: U.S. export restrictions and 'key recovery' policies are ineffectual as well as burdensome to business". Los Angeles Times. Retrieved December 14, 2015.
But recent advances in computing technology have rendered 40-bit encryption dangerously weak and export limits commercially obsolete.
References
- "Frequently Asked Questions (FAQ) About the Electronic Frontier Foundation's "DES Cracker" Machine". Electronic Frontier Foundation. July 16, 1998. Retrieved March 23, 2012.
- Grimmett, Jeanne J. (2001). Encryption Export Controls (pdf) (Report). Congressional Research Service Report RL30273.
{{cite report}}: Invalid|ref=harv(help) - Schneier, Bruce (1996). Applied Cryptography (Second ed.). John Wiley & Sons. ISBN 0-471-11709-9.
{{cite book}}: Invalid|ref=harv(help)