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2. Needham, R. A.; Schroeder, M. D. "Using Encryption for Authentication in Large Networks of Computers" Communications of the Association of Computing Machinery 21, 12; December 1978; pp. 995–999.
3. National Bureau of Standards. "The Data Encryption Standard." Federal Information Processing Standards Publication (FIPS PUB) 46; January 1977; National Technical Information Service, Springfield, Virginia.
4. National Bureau of Standards. "DES Modes of Operation." Federal Information Processing Standards Publication (FIPS PUB) 81; December 1980; National Technical Information Service, Springfield, Virginia.
5. National Bureau of Standards. "Guidelines for Implementing and Using the NBS Data Encryption Standard." Federal Information Processing Standards Publication (FIPS PUB) 74; April 1981; National Technical Information Service, Springfield, Virginia.