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Unformatted text preview: g questioned the security of DES . There has been much speculation on the key length, number of iterations, and design of the S-boxes. The S-boxes were particularly mysterious—all those constants, without any apparent reason as to why or what they’re for. Although IBM claimed that the inner workings were the result of 17 man-years of intensive cryptanalysis some people feared that the NSA embedded a trapdoor into the algorithm so they would have an easy means of decrypting messages. The U.S. Senate Select Committee on Intelligence, with full top-secret clearances, investigated the matter in 1978. The findings of the committee are classified, but an unclassified summary of those findings exonerated the NSA from any improper involvement in the algorithm’s design . “It was said to have convinced IBM that a shorter key was adequate, to have indirectly assisted in the development of the S-box structures and to have certified that the final DES algorithm was, to the best of their knowledge, free of any statistical or mathematical weaknesses” . However, since the government never made the details of the investigation public, many people remained unconvinced. Tuchman and Meyer, two of the IBM cryptographers who designed DES, said the NSA did not alter the design : Their basic approach was to look for strong substitution, permutation, and key scheduling functions.... IBM has classified the notes containing the selection criteria at the request of the NSA.... “The NSA told us we had inadvertently reinvented some of the deep secrets it uses to make its own algorithms,” explains Tuchman. Table 12.9 Commercial DES Chips Manufacturer AMD AMD AMD AT&ampT CE-Infosys Chip Am9518 Am9568 AmZ8068 T7000A SuperCrypt CE99C003 SuperCrypt CE99C003A Cry12C102 CA20C03A Year Clock Data Rate Availability 1.3 MByte/s 1.5 MByte/s 1.7 MByte/s 1.9 MByte/s 12.5 MByte/s 20.0 MByte/s N N N N Y 1981 3 MHz ? 4 MHz 1982 4 MHz 1985 ? 1992 20 MHz CE-Infosys 1994 30 MHz Y 1989 20 MHz 2.8 MByte/s 1991 25 MHz 3.85 MByte/s Newbridge CA20C03W 1992 8 MHz 0.64 MByte/s Newbridge CA95C68/18/09 1993 33 MHz 14.67 MByte/s Pijnenburg PCC100 ? ? 2.5 MByte/s Semaphore Roadrunner284 ? 40 MHz 35.5 Communications MByte/s VLSI VM007 1993 32 MHz 200.0 Technology MByte/s VLSI VM009 1993 33 MHz 14.0 Technology MByte/s VLSI 6868 1995 32 MHz 64.0 Technology MByte/s Western Digital WD2001/2002 1984 3 MHz 0.23 MByte/s Table 12.10 DES Speeds on Different Microprocessors and Computer...
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This note was uploaded on 10/18/2010 for the course MATH CS 301 taught by Professor Aliulger during the Fall '10 term at Koç University.
- Fall '10