[Cryptography] Simple non-invertible function?

[Krisztián Pintér]

On Mon, Sep 15, 2014 at 7:12 PM, Sandy Harris <sandyinchina at gmail.com> wrote:
> The function I need must take some amount of data in and put the same
> amount out.

there are plenty of pseudorandom permutations out there, like salsa
core (512 bit), cubehash core (1024 bit), keccak-f (25-1600 bit). you
can make a general prf out of them using:

Y = X + f(X)

where + is either xor or word-wise addition (of any word size).

disclaimer: i'm not a cryptographer, and i don't know if this
satisfies your security requirements. but i guess it does.