40-bit encryption
Template:Short description Template:DMCA 40-bit encryption refers to a (now broken) 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), 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.Lua error in package.lua at line 80: module 'Module:Footnotes/anchor_id_list' not found. 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,Lua error in package.lua at line 80: module 'Module:Footnotes/anchor_id_list' not found. and would be able to break 40-bit DES encryption in about two seconds.Lua error in package.lua at line 80: module 'Module:Footnotes/anchor_id_list' not found.
40-bit encryption was common in software released before 1999, especially those based on the RC2 and RC4 algorithms which had special "7-day" export review policies,[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."Lua error in package.lua at line 80: module 'Module:Footnotes/anchor_id_list' not found.Lua error in package.lua at line 80: module 'Module:Footnotes/anchor_id_list' not found. 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.[1][2] 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 factorization, 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
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- ^ Page Module:Citation/CS1/styles.css has no content.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.
- ^ Page Module:Citation/CS1/styles.css has no content.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
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- Page Module:Citation/CS1/styles.css has no content."Frequently Asked Questions (FAQ) About the Electronic Frontier Foundation's "DES Cracker" Machine". Electronic Frontier Foundation. July 16, 1998. Archived from the original on September 18, 2012. Retrieved March 23, 2012.
- Page Module:Citation/CS1/styles.css has no content.Grimmett, Jeanne J. (2001). Encryption Export Controls (PDF) (Report). Congressional Research Service Report RL30273. Archived from the original (pdf) on February 28, 2019. Retrieved July 26, 2011.
- Page Module:Citation/CS1/styles.css has no content.Schneier, Bruce (1996). Applied Cryptography (Second ed.). John Wiley & Sons. ISBN 0-471-11709-9.
