Proposal: API additions for determining curve support

[vcsjones]

Right now in netstandard1.6 we have ECCurve for using named or arbitrary ECC curves. This is very useful for certain type of applications where the curve is a configurable option (for example, a German company that insists on using brainpool curves for certain operations).

What we don't have right now is an easy way to list all of the supported named curves for a particular platform. Keeping with the brainpool example, Windows 10 supports most (if not all) of the named brainpool curves, however Windows 8.1 and below do not in CNG. Also, depending on how far #17597 goes, macOS CommonCrypto / Security Transforms do not support curves other than the standard NIST prime curves and some of djb's curves.

I'm not entirely sure all platforms support arbitrary curves, either (for example, Twisted Edwards curves).

I would then propose an API that lets us determine the capabilities of the current platform.

[vcsjones]

/cc @bartonjs

[vcsjones]

I'm no longer invested in this proposal, and given the lack of discussion on it, I am going to close this out.