If the crypto/implementation turns out to be unsound, first you have to 1. learn that the flaw exists, and then 2. take steps to remedy the situation. That's a

If the crypto/implementation turns out to be unsound, first you have to 1. learn that the flaw exists, and then 2. take steps to remedy the situation. That's a window of opportunity where "obscurity" can potentially buy you time. On the other hand, if you assume your public keys are widely known and distributed, you're more likely to drop everything and take care of step 2 ASAP. So maybe it's a wash...