Wikipedia:Reference desk/Archives/Computing/2016 April 27

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April 27

Block ciphers with key-dependent S-boxes

Blowfish (cipher) and Twofish have key-dependent S-boxes. Are there any other block ciphers with this trait? Johnson&Johnson&Son (talk) 05:40, 27 April 2016 (UTC)

Isn't that rather common? AES has key-dependent S-boxes and every year there are at least a hundred people who make up their own version of AES and continue to use key-dependent S-boxes. 209.149.115.199 (talk) 12:50, 27 April 2016 (UTC)

AES has a fixed S-box. Rijndael with a different S-box may be secure but isn't AES. I think you can replace the S-box in any cipher that has one, so the question is meaningless unless it's limited to variants that have some sort of official status. -- BenRG (talk) 22:27, 27 April 2016 (UTC)

You can replace the fixed S-box of any cipher that has fixed S-boxes. But I really don't see how you can replace the fixed S-boxes of existing ciphers with key-dependent S-boxes, since the key schedule doesn't provide a way to key them. So no, the question is not meaningless. Johnson&Johnson&Son (talk) 02:08, 28 April 2016 (UTC)

It is trivial to turn a fixed S-box into a key-dependent S-box. You calculate the S-boxes first, then do the encryption/decryption. The specific S-boxes in the United States federally accepted AES are fixed, but that doesn't mean that you have to use those S-boxes and ONLY those S-boxes. Those are just ones that have been tested to do well. You can use your own or make them on the fly using keys. 209.149.115.199 (talk) 16:23, 28 April 2016 (UTC)

Khufu and REDOC II are two. Also, Applied Cryptography describes IDEA's multiplication mod 2¹⁶+1 as a key-dependent S-Box. -- BenRG (talk) 22:27, 27 April 2016 (UTC)

Mercy (cipher) -- Finlay McWalter··–·Talk 22:46, 27 April 2016 (UTC)

Searching for a nonexistent website

File:BELLE AIRE House in Roanoke VA.jpg claims that its source is the "Deyerle Family Association Website", and no evidence of proof is provided, so it's time for Commons:Template:npd. However, I figured I'd just find the website, and if the photo were still there, I could add a link as a rationale for speedy deletion. Problem: the website doesn't seem to exist, even though I found other online references to it, so I suppose it's been dead for a while. Is there a way to find a no-longer-extant website when nobody mentions a URL? Google won't provide long-dead URLs, and the Internet Archive requires the URL in the first place. In the end, I found a Geocities link through [1], but aside from its front page, it never got accessed by the Internet Archive, so this is now more of a general question than a help-me-with-this-specific-file question. Nyttend (talk) 12:08, 27 April 2016 (UTC)

I recommend time-travel (in either direction!) --Tagishsimon (talk) 12:35, 27 April 2016 (UTC)

PC video game

My Tom Clancy's H.A.W.X 2 not working, its telling me to play it online. Any idea why? -- Apostle (talk) 20:09, 27 April 2016 (UTC)

Its developed and published by Ubisoft. This company has a history of exessive software protection, including enforcing an online connection to to play even if you dont play multiplayer. --Kharon (talk) 01:47, 28 April 2016 (UTC)

Okay thank you -- Apostle (talk) 07:33, 28 April 2016 (UTC)