I am working in a very bandwidth restricted environment, and we are looking to implement ECDSA digital signatures. Although they are no longer recommended, we might be looking to use curves that are not listed as supported by most libs, including OpenSSL: https://en.wikipedia.org/wiki/Comparison_of_TLS_implementations#Supported_elliptic_curves
We are looking at curves such as secp112r2, secp128r1, sect131r1 and so on. This is not to discuss security of these, but their support.
In Cygwin, a huge load of curves is available, including the mentioned low-secutity curves. But in the URL these curves are not listed. Our team has observed that in some other OpenSSL sources (that are not through Cygwin), these curves are not supported. Are they no longer supported by OpenSSL, and if so - why are they available to me through Cygwin?
And by the way - I assume curve support is rather complicated, so that it is not possible to "import" a curve that is not supported in a given library.