rot13

This is just a simple ROT13 encoder / decoder (i.e. alphabetical shift cypher with a shift value of 13 so that the encoder and decoder is exactly the same).

It is probably close to being optimally coded in Matlab, but if it actually isn't, it's still useful for reading some comments in Slashdot :)

As for features, it preserves type case and non-alphabetical characters, and the alphabetical shift can be specified.

See cryptoshift, cryptosub and cryptodesub by Bill Higley if you want a more general shift cypher / substitution function.