NIBBLE_MASK
if (!slh_wots_chain(ctx, sk, 0, NIBBLE_MASK, pk_seed, adrs, tmp_wpkt))
NIBBLE_MASK - msg_and_csum_nibbles[i],
*out++ = (*in++ & NIBBLE_MASK);
csum = (uint16_t)(NIBBLE_MASK * in_len) - csum;
out[0] = (csum >> (2 * NIBBLE_SHIFT)) & NIBBLE_MASK;
out[1] = (csum >> NIBBLE_SHIFT) & NIBBLE_MASK;
out[2] = csum & NIBBLE_MASK;