Talk:Skipjack (cipher)

Strong enough for what?

The comment here about exactly strong enough is confusing. At least to me. Strong enough to do what? or be what? Perhaps this is a suggestion that NSA was able to cryptanalyze it, but didn't think anyone else would be able to? Is this a quote from someone?

Anyone who can enlighten, please speak up.

ww 18:06, 17 Apr 2004 (UTC)

We should perhaps rephrase it; it is a quote (from the paper ref'd, I think). Because there is an attack on 31 rounds, and not on the full 32-rounds, it seems as if Skipjack is strong enough to resist cryptanalysis, but "only just". i.e. there's no "safety margin". — Matt 18:13, 17 Apr 2004 (UTC)

Ah... Then we should say something about there has been speculation that NSA knew there was no safety margin (but will have to explain that or it will be opaque) and may have designed the algorithm accordingly.

I don't think I'm comfortable with this. There is lots of ascription of motive in a complex and contingent on the state of the art (unknowable) engineering arena.

Just call me Burdan's donkey for the moment. ww 18:23, 17 Apr 2004 (UTC)

Matt, Your refactoring of the text is a considerble improvement. I'm still dubious about motive ascription here, but I can live with what we have. Well done. ww 19:36, 17 Apr 2004 (UTC)

Thanks; I've just added a new "Cryptanalysis" section; hopefully I'll be able to flesh out these "stub" sections soon. Also, I've removed the "quote", because I can't find it in the original paper. (See if I can dig it out from elsewhere, because it rings a bell...) — Matt 19:45, 17 Apr 2004 (UTC)

Schneier suggestion about adopting Skipjack as a standard

I can't verify the below suggestion; anyone have a source? Schneier's Crypto-gram article implies that he has a different theory to this.

Some, including Bruce Schneier, have suggested this was done as a part a NSA initiative to have Skipjack adopted as a standard encryption algorithm.

— Matt 10:04, 18 Apr 2004 (UTC)

Matt, It was my memory of Scheier's account from which I wrote this. You seem to have checked Schneier and I've summarized it wrongly, I take it? I've made a note to check for myself. ww 17:34, 18 Apr 2004 (UTC)

There's a link at end of article to the only Schneier comment I could find — Matt 17:38, 18 Apr 2004 (UTC)

Matt, Mea culpa. That was (I'm pretty sure) what I had in mind. Wider adoption of Skipjack by various folks isn't exactly a standard is it? ww 18:32, 18 Apr 2004 (UTC)

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This page was originally called Skipjack encryption algorithm, to disambiguate it from the fish. I am a little puzzled why it was moved to plain "Skipjack" when roughly half the links to the new name actually refer to the fish. Is there some reason we can't make this a dab page, and move this article back to something specifically cipher-ish? Securiger 07:51, 19 Apr 2004 (UTC)

Oops — I didn't realise it was also a fish! (Also various boats, it seems). Skipjack (cipher) would bring it in line with the other dab'd ciphers — Matt 10:40, 19 Apr 2004 (UTC)

32 rounds still secure

The article claims that there is a slide attack on 32 rounds of Skipjack. Are you sure? I can't think of what that might refer to. I think the claim should be deleted; it does not sound right to me, and I consider myself reasonably familiar with the research literature on cryptanalysis of Skipjack. Also, it is not documented or cited, which further strengthens my skepticism.

63.197.31.112 (talk) 00:29, 4 August 2010 (UTC)

31 nearly secure

Guys, the paper attacking 31 rounds clearly states that their attack is only slightly better than brute-force checking of all the keys. I've added a comment. I hope you approve.

Max —Preceding unsigned comment added by 193.205.213.166 (talk) 04:58, 20 September 2010 (UTC)

The fact that it breaks 31 rounds, not 32, means it's a theoretical attack to begin with and can't be applied to the real cipher. How fast it is, is mostly irrelevant to theoretical attacks. -- intgr [talk] 20:15, 21 September 2010 (UTC)

Knudson and Wagner's On the structure of Skipjack, Discrete Applied Mathematics 111 (2001) 103–116, is the more definitive reference about Skipjack. Skipjack is a very odd example of an unbalanced feistel network because it changes half of the block each round and only uses part of source block in each round. The key insight into Skipjack is that rule B is a permuted version of the Rule A decryption round. This causes the cipher to be equally strong in both the encrypting and decrypting directions, which probably explains why all the attacks on skipjack never quite make it, despite the round function being weird and the key schedule weak. 24.91.50.90 (talk) 07:27, 23 April 2013 (UTC)

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