I'm looking for a hashing algorithm that will take an input of 16 chars string, and output a different string of 16 chars. [that can't be converted to the original string]
I've thought of taking a MD5 result and slice the first 16 chars, but i think it is not the right way to solve the problem, since it looses the hashing idea.
any suggestions? platform, if matters, is Python.
Actually, you lose the hashing idea already when you decide input size needs to match the output size, as, according to Wikipedia "A hash function is any function that can be used to map digital data of arbitrary size to digital data of fixed size."
If you are building a credit card number tokenization system, just make up a random string after checking the number has not already been tokenized, check that the token does not have a collision, save the original number in the ways allowed by PCI standards (read them, https://www.pcisecuritystandards.org/documents/Tokenization_Guidelines_Info_Supplement.pdf) and you are good to go.
If not, a chopped hash function like SHA256 or MD5 will give repeatability outside your system too and risk of collisions (that's part of it being hashing), but whether those make sense to use really depends on your use case.