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Rot13 is not a hashing algorithm. A hashing algorithm is a one-way function where many entities in the input domain map to the same entity in the output codomain. This means if you have the hash you can't determine the input with out making a guess.

Rot13 is a function with a one to one mapping between the domain and codomain. If you have the output you can apply a function to get the input.

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Not sure why the downvotes. Comradesmith's assessment of rot13 is absolutely correct. Clearly rot13 is more like PGP, in that you can recover the plain text from cypher text.

But you don't care about finding the original password. You only care about finding a string that after applying the hash function, gives the same out.

That's why you can have a hash function like h(x) = 0, whose value gives you no information about x, and still not being able to use it.

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