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Yeah the NSA modified the DES S-Box in its development, they made the final tweeks to the GSM A5/1 algorithm, another person points out the Clipper Chip, etc.
by davidj 16y ago
Yeah the NSA modified the DES S-Box in its development, they made the final tweeks to the GSM A5/1 algorithm, another person points out the Clipper Chip, etc. You are clueless if you didn't know these things, do you think the NSA just sits on their butt?
- tptacek 16y agoThe NSA is believed to have strengthened DES by making its substitutions more resilient against differential cryptanalysis. Careful with with words like "clueless". On this point I'm inclined to agree with Schneier: why inject backdoors into things, leaving fingerprints and betraying both opsec and tradecraft, when you can just sit back and watch the software companies build the backdoors for you? NSA has as much as come out and said this at keynote speeches already, but it seems pretty obvious from my vantage point.
- davidj 16y ago"The NSA is believed to have strengthened DES" No they didn't they cut the key size in half, and where can I find on a source that shows me that the s-box changes were intended to make DES stronger?
- tptacek 16y agoAlan Konheim (one of the designers of DES) commented, "We sent the S-boxes off to Washington. They came back and were all different." [...] Some of the suspicions about hidden weaknesses in the S-boxes were allayed in 1990, with the independent discovery and open publication by Eli Biham and Adi Shamir of differential cryptanalysis, a general method for breaking block ciphers. The S-boxes of DES were much more resistant to the attack than if they had been chosen at random, strongly suggesting that IBM knew about the technique back in the 1970s. I'm done bickering about trivia, though. If you'd like the last word, as long as you don't say anything overtly stupid, I'm not going to respond. Happy holidays!