gen_chain
gen_chain(pk+i*params->n, pk+i*params->n, 0, params->w-1, params, pub_seed, addr);
gen_chain(sig+i*params->n, sig+i*params->n, 0, basew[i], params, pub_seed, addr);
gen_chain(pk+i*params->n, sig+i*params->n, basew[i], params->w-1-basew[i], params, pub_seed, addr);