Talk:Caesar cipher

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Contents

1 Key space 2 Explaining revert 3 Inventor? 4 Cryptanalysis 5 Good job 6 Fixed example 7 Advanced Breaker

Key space

what is key space in caesar cipher?

The set {1, 2, ... 26}, being all the possible offsets. Not much of a challenge, even for a human computer! --Robert Merkel 23:49 29 Jun 2003 (UTC)

Actually, it is only the set {1 ... 25} - ROT26 not being much of a cipher :) - Marcika 02:18, 12 Apr 2005 (UTC)

Explaining revert

A cryptogram (in the English meaning) and a cryptic crossword are not the same kind of puzzle at all. A cryptic crossword is a crossword with particular styles of clues. It does not involve any encryption. A cryptogram is a piece of text which has been encrypted with a simple substitution cipher (each letter replaced throughout with some other letter). It's meant to be solved by frequency analysis and recognizing letter patterns.

(If, as the cryptic crossword page suggests, those are called "cryptograms" in Dutch, that might be part of the confusion. The intended reference in this article is to what is called a cryptogram in English.) --FOo

Inventor?

Others are known to have used such ciphers before Caesar, so it was certainly not invented by him.

I've had a quick thumb through Kahn (and the Internet), but I can't find any reference to shift ciphers before Caesar; I don't think we can say "certainly not invented by him", or can we? An NSA page (admittedly for kids) attributes it to him: http://www.nsa.gov/kids/ciphers/ciphe00002.htm — Matt 04:57, 2 Aug 2004 (UTC)

Matt, The timeline in progress notes earlier uses of single alphabet substitution cyphers (eg, Atbash) and I think I remember that the Egyptian carving thing from thousands of years earlier was such a thing (but don't count on it). The problem would seem to be that many things get attributed to the powerful and famous (just consider authorship credits on papers written by graduate students, no), and this pollutes the attribution space with lots of squirrely data. JC would seem to have been an enthusiastic user in a military context and a powerful and famous guy generally, so things may have stuck. That we no longer have that Roman book on crypto is unfortunate for this. If we simply say that single alph sub cypher wasn't his, we would certainly be safe. ww 16:27, 2 Aug 2004 (UTC)

I've added a (somewhat cautious) replacement. — Matt 00:58, 3 Aug 2004 (UTC)

Cryptanalysis

The History section relates cryptanalysis of the caesar cipher and frequency analysis. That's the nice way to do it, but since brute force is so trivial and obvious for this cipher, can we really even talk about "methods of breaking the cipher" being unavailable? I mean, it's a *Caesar cipher*. :) Lunkwill 21:21, 2 Aug 2004 (UTC)

Sure ;) I presume you're referring to "furthermore, there is no record that any method was then known which would reliably break such a cipher". Perhaps here, though, it was assumed that "the enemy doesn't know the system", in which case frequency analysis would be very useful. — Matt 00:49, 3 Aug 2004 (UTC)

Hmm..yeah, having thought about it, perhaps this cryptanalysis section would be better merged into frequency analysis or substitution cipher; most of it is pretty general. — Matt 00:45, 24 Nov 2004 (UTC)

Good job

I just wanted to congratulate the authors of this article. Although a very simple topic, they've really done a great job of explaining it while using it as a demonstration of simple cryptography and cryptanalysis. I'm impressed. Deco 03:24, 12 Apr 2005 (UTC)

Thanks for your kind comments! — Matt Crypto 12:02, 12 Apr 2005 (UTC)

Fixed example

One of the examples in the article stated that "AFCCQ" would rotate to either "jolly" or "cheer". It doesn't; it rotates to "jollz" and "chees". I fixed the example to read "AFCCP" instead. This is my first edit of a featured article in particular, so I hope I wasn't meant to go through any sort of process for it; something I only thought about after I'd done so. --Ciaran H 15:14, Apr 12, 2005 (UTC)

Thanks for spotting this! I copied it mindlessly from Bauer's Decrypted Secrets without checking. Do the other ones work? You are most definitely allowed to change even featured articles, and especially if they've got (cough) mistakes in them ;-) While checking, I also noticed that "AFCCP" could also become "diffs" (which isn't a dictionary word, of course, but it's a common bit of jargon on Wikipedia and elsewhere). — Matt Crypto 15:23, 12 Apr 2005 (UTC)

Ha! I love it when I find mistakes in published books. :P As far as I can see, the others are fine, although I wonder at the "attackatonce" example table, as the shifts are in reverse order. From "exxegoexsrgi", the text "attackatonce" would technically be a shift of 22, not 4. Or am I misreading something? --Ciaran H 15:32, Apr 12, 2005 (UTC)

It depends which way you're looking at it: if you're viewing it as a brute force attack, you're trying each possible encryption key (right shift), and decrypting the ciphertext with it — a decryption is a shift in the opposite direction to encryption (left shift). I've changed the heading of the table, hopefully it makes it clearer? — Matt Crypto 15:43, 12 Apr 2005 (UTC)

It makes sense now, yes, but now it seems that the column is too wide. Would just "Decryption shift" or "Reverse shift" work? --Ciaran H 15:48, Apr 12, 2005 (UTC)

I've changed it to "Decryption shift", which is a bit smaller. — Matt Crypto 15:55, 12 Apr 2005 (UTC)

Sounds good. I also right-aligned the numbers so that it looks better. Are you happy with this? --Ciaran H 15:59, Apr 12, 2005 (UTC)

I've tried central alignment, which (personally) I think looks slightly better in the wide column, but I don't really mind much either way. — Matt Crypto 16:04, 12 Apr 2005 (UTC)

Centre alignment works too. ;) Would it be worth centering the plaintext as well? --Ciaran H 16:05, Apr 12, 2005 (UTC)

Might as well - done. — Matt Crypto 16:09, 12 Apr 2005 (UTC)

Advanced Breaker

Where could I find an advanced caesar Cipher breaker? I need it to figure out strings such as delta=-?,+?,-?,+?,-?,+?,... and possibly do it backwards for me too. I have no idea where to even begin to break a cipher in which the delta is unknown!!! Jaberwocky6669 05:06, Jun 21, 2005 (UTC)

I presume you aren't talking about the Caesar cipher as described in this article, because the article goes into quite some detail about how to break those...perhaps you mean a shift cipher where the shift can vary with each letter, as opposed to being fixed? If the shift varies according to a repeating keyword, the scheme is usually called a Vigenere cipher. Have I understood correctly what you're describing? — Matt Crypto 13:57, 21 Jun 2005 (UTC)

• You understood puuurrfectleee... thanks! I am trying to solve an internet riddle thingie lol... Jaberwocky6669 18:46, Jun 22, 2005 (UTC)