OpenSSL: Is it possible to view the EC Named Curve without the ecparam file?

Question

Is there an OpenSSL command to derive the Named Curved that was used in the generation of an EC Key Pair?

I generate the parameters into a PEM file here:

openssl ecparam -name secp256k1 -out secp256k1.pem

Then verify the Named Curve used by typing:

openssl ecparam -in secp256k1.pem -text -noout

But how to achieve the same when you have only the Private.pem and Public.pem and NOT the ecparam file?

openssl pkey -in user1Key.pem -text -noout worked on keys I generated with the Command-Line OpenSSL tool but not the C libraries. When I run this command against the PEM files - I generated using C - I get everything but NOT the short ecparam name. I get the Private, Public, Seed, Prime, A, B, etc.

Answer 1

Update:

My C code was generating an EC Pair with OpenSSL APIs where the explicit parameters for the Curve was set. When I did the same with OpenSSL's command line tool, I did not set the explicit parameter.

To get around the issue - to verify both sides were deriving the same Key - I used the following OpenSSL command line tool:

openssl ecparam -in ec_paramprime256v1.pem -genkey -noout -out appKey.pem -param_enc explicit

If this has impacted you, I suggest you investigate OpenSSL's wiki for set_asn1_flag