I'd like to test and see if certain software uses P-521 ECC curves, or if it uses another variant.
Without having access to the sourcecode, or the specification, is there any way for me to test which ECC curve a given implementation of software uses?
Take a x509 certificate as an example, aside from ASN.1 information that may exist in the file, is there any way to look at raw cryptographic outputs and determine the curve used?
What is the minimum information needed to understand what curve is being used? (What variables on the client, or on the issuer/CA are needed)?