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Is it possible to do web searches for ROT13 text?

I guess you could type in the literal ROT13'd text you're after, but that'd only cover exact matches.

Background: Became curious once I did a ROT13 tweet about a tv program being a mockumentary.

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are you looking for a method to do this with Google, Bing, or some other existing service, or are you just looking for a treatise on the theoretical is it possible question? this site is for questions that are fairly concrete, and so far i don't see it in this one. the latter might be reasonable for Stack Overflow if you tag it [algorithms] though. –  quack quixote Apr 1 '10 at 12:03
    
@quack: searching the web using an existing service. –  Andrew Grimm Apr 2 '10 at 1:29

3 Answers 3

Rot-13 is a simple substitution cipher that can be readily cryptanalyzed, using paper-and-pencil techniques.

These techniques would allow you to look for common plaintext words (such as "the", "a", "is", etc. in English) encoded (or enciphered) using Rot-13.

Because of the simplicity of the substitution cipher it does not conceal natural language characteristics, such as letter frequency, so you could analyze a page or text looking at the letter frequency of the plaintext natural language (e.g. English, Dutch) as encoded by Rot-13.

For example 'e' is the most common letter in English writings, so you would expect 'r' to be the most common letter (on average) of Rot-13 English text. Followed by 'g' (plaintext: t), 'n' (a), and 'b' (o).

This would be simple to write a WWW search spider to look for, but somewhat tedious to manually use existing online search engines (i.e. Google, Cuil, or Yebol).

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nice answer .... –  ldigas Apr 1 '10 at 16:58

One way to get a decent idea whether the text is ROT13 encoded would be to search for common sequences/words.

For instance, if you were looking for ROT13 english text you could search for:

gur bs gb naq n va vf vg lbh gung

which is the top ten english words according to world-english.org:

the of to and a in is it you that

http://www.google.com/search?hl=en&lr=&q=gur+bs+gb+naq+n+va+vf+vg+lbh+gung&aq=f&aqi=&aql=f&oq=&gs_rfai=

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You can in your defined way. Rot13 have no special characters like base64, or other algorithms, which can define rot13 text.

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I spoked about this I guess you could type in the literal ROT13'd text you're after, but that'd only cover exact matches.. He can do that! Or I am wrong? –  lfx Apr 1 '10 at 17:03
    
Yes, he can. I thought you wrote "You can/cannot in a defined way." Which when combined with your second sentence as evidence (lack of standard header) would make sense. Sorry for the confusion. –  mctylr Apr 1 '10 at 18:03

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