SJSU CS 265 - DES and TDES (6 pages)

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DES and TDES



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DES and TDES

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Pages:
6
School:
San Jose State University
Course:
Cs 265 - Cryptography and Computer Security
Cryptography and Computer Security Documents

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Analyzing DES and TDES Rukman Senanayake CS265 Cryptography and Computer Security Spring 2005 DES The History In the early 1970s it was recognized that a common encryption standard is required in the commercial world due to increased use of computer networks by banks and other commercial enterprises Until then cryptography was a domain restricted to the military and the diplomatic community The most radical characteristic of this requirement was that the encryption algorithm needed to be public knowledge since it needs to allow interoperability among various enterprises In an era where secrecy was synonymous with cryptography this indeed was a radical deviation from the common mind set The National Bureau of Standards NBS invited proposals for a cryptographic standard and received only one serious submission the Lucifer algorithm developed by IBM IBM s submission was tweaked by the NSA and the reasons for modifying the algorithm remained undisclosed for a long time This immediately sparked off a heated debate regarding hidden trap doors in DES using which the NSA could decrypt cipher text without the original key being known This large outcry among those who paid attention to the new standard keeping in mind at this time the field of cryptography itself was in its infancy grew louder as NSA refused to provide a rationale for the changes The situation was exacerbated by the fact that one of the modifications was to shorten the length of the key used in the algorithm Two main characteristics determine the strength of a cryptographic algorithm 1 The mathematics on which the algorithm is based upon 2 The length of the key used by the algorithm If the key length is long enough it is impossible even with a cluster of supercomputers to break a cryptographic algorithm by searching for keys in a brute force fashion In most cases modern cryptographic algorithms are fitted with a key long enough to deter any brute force attack Due to this the modifications done by NSA caused a



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