def fe_step_unstep
import bend-osdev-cipher-core@0.1.0.0/PROOF.bend as PROOFimport Base
import bend-osdev-cipher-core@0.1.0.0/cipher_core.bend as L
82def fe_step_unstep(~RK: Data, ~f: RK -> U32 -> U32, +k: RK, b: L.LcBlock64) -> {b == L.lc.fe.step(~RK, ~f, k, L.lc.fe.unstep(~RK, ~f, k, b)) : L.LcBlock64}:
83 match b:
84 case L.LcBlock64{+l, r}:
85 %u32_xx(r, f(k, l)) : {L.LcBlock64{l, r} == L.LcBlock64{l, _} : L.LcBlock64}
86 {==}