I have signed no contracts or agreements whose existence I cannot mention.
They thought they found in numbers, more than in fire, earth, or water, many resemblances to things which are and become; thus such and such an attribute of numbers is justice, another is soul and mind, another is opportunity, and so on; and again they saw in numbers the attributes and ratios of the musical scales. Since, then, all other things seemed in their whole nature to be assimilated to numbers, while numbers seemed to be the first things in the whole of nature, they supposed the elements of numbers to be the elements of all things, and the whole heaven to be a musical scale and a number.
I think this fails to say how the analogy of cryptography transfers to metaethics. What properties of cryptography as a field make it such that you cannot roll your own. Is it just that many people have the experience of trying to come up with a croptographic scheme and failing, meanwhile there are perfectly good libraries nobody has found exploits to yet?
That doesn’t seem very analogous with metaethics. As you say, it is hard to decisively show a metaethical theory is “wrong”, and as far as I know there is no well-studied metaethical theory which has no exploits yet.
So what exactly is the analogy?