--curves

Set specific curves to use during SSL session establishment according to RFC 8422, 5.1. Multiple algorithms can be provided by separating them with : (e.g. X25519:P-521). The parameter is available identically in the OpenSSL s_client and s_server utilities.

--curves allows a OpenSSL powered curl to make SSL-connections with exactly the (EC) curve requested by the client, avoiding nontransparent client/server negotiations.

If this option is set, the default curves list built into OpenSSL are ignored.