pygfc 0.2.1

Implementation of a Generalized-Feistel Cipher for generating random permutations.

gfc

Implementation of a Generalized-Feistel Cipher [1, alg. 3] for generating random permutations.
It uses Speck 64/128 as the random function, and can generate permutations up to 2^64.

C API

#include <gfc/gfc.h>
GFC* gfc_init(uint64_t range, uint64_t rounds, uint64_t seed);
void gfc_destroy(GFC* gfc);
uint64_t gfc_decrypt(const GFC* gfc, uint64_t m);
uint64_t gfc_encrypt(const GFC* gfc, uint64_t m);

Python API

from pygfc import Permutation
# Permutation(range, rounds, seed)
perm = Permutation(2 ** 16, 8, 42)
assert set(perm) == set(range(2 ** 16))
assert all(perm.inv(perm[i]) == i for i in range(2 ** 16))

Dependencies

The Speck implementation is from madmo/speck and is licensed under the ISC license (MIT-compatible).

References

[1] Black, John, and Phillip Rogaway. "Ciphers with arbitrary finite domains." Cryptographers’ track at the RSA conference. Springer, Berlin, Heidelberg, 2002. https://web.cs.ucdavis.edu/~rogaway/papers/subset.pdf