This is an encryption algorithm commonly used for hiding information in [usenet] posts that is open to all but not immediately readable. An example is posting about film endings, or example answers.

The algorithm is actually a [caesar] cipher with a 13 place rotation. This number is special because in an alphabet with 26 letters, caesar 13 and caesar -13 use the same map, so the same call can be used for encoding and decoding. ([RS])

Using '''tr''' from [Example scripts everybody should have], a rot13 cipher can be written as easily as
 puts [tr A-Za-z N-ZA-Mn-za-m {Guvf vf n grfg}]
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So, using rot13, "fnynq" is caesar salad. --[CLN]
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[KBK] - Any monoalphabetic substitution cipher is, of course, trivial
to break.  [Solving cryptograms] written in such ciphers is well within
the compass of Tcl's capabilities.

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See also [vignere], [caesar], [uuencode], [base64] 

[Category Package] [Category Cryptography]