curl/docs/cmdline-opts/curves.md

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c: Copyright (C) Daniel Stenberg, daniel@haxx.se, et al. SPDX-License-Identifier: curl Long: curves Arg: Help: (EC) TLS key exchange algorithms to request Protocols: TLS Added: 7.73.0 Category: tls Multi: single See-also:

• ciphers Example:
• --curves X25519 $URL ---

--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.