A tiny pseudorandom permutation generator library

libtprpg implements a pseudorandom permutation generator based on the generalized feistel cipher algorithm described by John Black and Phillip Rogaway in their paper "Ciphers with Arbitrary Finite Domains". See also

http://blog.notdot.net/2007/9/Damn-Cool-Algorithms-Part-2-Secure-permutations-with-block-ciphers

I make no claims as to the security of this implementation, it was designed to be simple first and foremost. The round function is based on XTEA and the key scheduling algorithm is based on RC4. Both XTEA and RC4 have know issues, though libtprpg uses them in a way which should prevent any known attacks from being applicable. One could easilly change the KSA and/or round function - a more conservitive but still small/simple design would use siphash as the round function and hkdf/siphash as the KSA.

Take a look at tprpg.h and the included tprpg, cards, and blackjack examples. Don't use this for anything security sensitive unless your have someone more qualified than me evaluate it (and if you do, it would be awsome if you shared the results).

Just drop tprpg.c and tprpg.h into your project. This is acceptable even for closed source commercial projects. See the LICENSE file for details.