CDMF
{{Short description|Cryptographic algorithm}}
In cryptography, CDMF (Commercial Data Masking Facility) is an algorithm developed at IBM in 1992 to reduce the security strength of the 56-bit DES cipher to that of 40-bit encryption, at the time a requirement of U.S. restrictions on export of cryptography. Rather than a separate cipher from DES, CDMF constitutes a key generation algorithm, called key shortening. It is one of the cryptographic algorithms supported by S-HTTP.
Algorithm
Like DES, CDMF accepts a 64-bit input key, but not all bits are used.
The algorithm consists of the following steps:
- Clear bits 8, 16, 24, 32, 40, 48, 56, 64 (ignoring these bits as DES does).
- XOR the result with its encryption under DES using the key 0xC408B0540BA1E0AE.
- Clear bits 1, 2, 3, 4, 8, 16, 17, 18, 19, 20, 24, 32, 33, 34, 35, 36, 40, 48, 49, 50, 51, 52, 56, 64.
- Encrypt the result under DES using the key 0xEF2C041CE6382FE6.
The resulting 64-bit data is to be used as a DES key. Due to step 3, a brute force attack needs to test only 240 possible keys.
References
- {{cite journal
|author1=D.B. Johnson |author2=S.M. Matyas |author3=A.V. Le |author4=J.D. Wilkins | title = The Commercial Data Masking Facility (CDMF) data privacy algorithm
| journal = IBM Journal of Research and Development
| volume = 38
| issue = 2
| pages = 217–226
| publisher = IBM
| date = March 1994
| url = http://domino.watson.ibm.com/tchjr/journalindex.nsf/0/a453914c765e690085256bfa0067f9f4?OpenDocument
| format = PDF
| accessdate = April 11, 2007
| doi = 10.1147/rd.382.0217 | url-access = subscription
}}
- {{US patent|5323464}}, IBM's patent on CDMF
- [https://web.archive.org/web/20051016075352/http://www.isg.rhul.ac.uk/~cjm/ISO-register/0005.pdf ISO/IEC9979-0005 Register Entry (PDF)], registered October 29, 1994
- {{cite book
| last = Schneier
| first = Bruce
| authorlink = Bruce Schneier
| title = Applied Cryptography
| url = https://archive.org/details/appliedcryptogra00schn
| url-access = limited
| edition = 2nd
| publisher = John Wiley & Sons
| date = 1996
| page = [https://archive.org/details/appliedcryptogra00schn/page/n1000 366]
| isbn = 0-471-11709-9 }}
- {{IETF RFC|2660}}, defines S-HTTP
{{DEFAULTSORT:Cdmf}}
Category:Cryptographic algorithms
Category:Data Encryption Standard
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