hash_df
static void hash_df(secret void *, size_t, const struct hvec *, size_t);
hash_df(D->V, sizeof D->V, seed_material, arraycount(seed_material));
hash_df(D->C, sizeof D->C, hv, arraycount(hv));
hash_df(seed, sizeof seed, seed_material, arraycount(seed_material));
hash_df(D->C, sizeof D->C, hv, arraycount(hv));