I am trying to find the sub keys of a FEAL-4 cipher. I am able to get a number of possibilities for $K_0$ after using Michael Stamps formula using a as a constant and going through $2^{32}$ keys. The problem is that I don't know what to do next as it isn't in any of the literature.
Stamps formula for a constant is
$$a = S23,29(L_0 \oplus R_0 \oplus L_4) \oplus S31(L_0 \oplus L_4 \oplus R_4) \oplus S31(F(L_0 \oplus R_0 \oplus K_0))$$
Looking for $K_1$ to $K_5$.
The FEAL-4 steps are:
