curl/docs/cmdline-opts/curves.md

---
c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
SPDX-License-Identifier: curl
Long: curves
Arg: <list>
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.
docs/cmdline: change to .md for cmdline docs - switch all invidual files documenting command line options into .md, as the documentation is now markdown-looking. - made the parser treat 4-space indents as quotes - switch to building the curl.1 manpage using the "mainpage.idx" file, which lists the files to include to generate it, instead of using the previous page-footer/headers. Also, those files are now also .md ones, using the same format. I gave them underscore prefixes to make them sort separately: _NAME.md, _SYNOPSIS.md, _DESCRIPTION.md, _URL.md, _GLOBBING.md, _VARIABLES.md, _OUTPUT.md, _PROTOCOLS.md, _PROGRESS.md, _VERSION.md, _OPTIONS.md, _FILES.md, _ENVIRONMENT.md, _PROXYPREFIX.md, _EXITCODES.md, _BUGS.md, _AUTHORS.md, _WWW.md, _SEEALSO.md - updated test cases accordingly Closes #12751 2024-01-21 06:18:43 +08:00			`---`
copyright: update all copyright lines and remove year ranges - they are mostly pointless in all major jurisdictions - many big corporations and projects already don't use them - saves us from pointless churn - git keeps history for us - the year range is kept in COPYING checksrc is updated to allow non-year using copyright statements Closes #10205 2023-01-02 20:51:48 +08:00			`c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.`
docs/cmdline-opts: add copyright and license identifier to each file gen.pl now insists on C: and SPDX-License-Identifier: fields to be present in all files. Closes #9002 2022-06-14 06:12:03 +08:00			`SPDX-License-Identifier: curl`
tls: add CURLOPT_SSL_EC_CURVES and --curves Closes #5892 2020-08-29 20:09:24 +08:00			`Long: curves`
cmdline-opts: shorter help texts In an effort to increase the readability of the "--help all" output on narrow (80 column) terminals. Co-authored-by: Jay Satiro Closes #13169 2024-03-25 17:02:30 +08:00			`Arg: <list>`
			`Help: (EC) TLS key exchange algorithms to request`
tls: add CURLOPT_SSL_EC_CURVES and --curves Closes #5892 2020-08-29 20:09:24 +08:00			`Protocols: TLS`
			`Added: 7.73.0`
docs: add categories to all cmdline opts Adapted gen.pl with 'listcats' This commit is a part of "--help me if you can" Closes #5680 2020-07-13 20:15:04 +08:00			`Category: tls`
cmdline/docs: add a required 'multi' keyword for each option The keyword specifies how option works when specified multiple times: - single: the last provided value replaces the earlier ones - append: it supports being provided multiple times - boolean: on/off values - mutex: flag-like option that disable anoter flag The 'gen.pl' script then outputs the proper and unified language for each option's multi-use behavior in the generated man page. The multi: header is requires in each .d file and will cause build error if missing or set to an unknown value. Closes #9759 2022-10-18 16:39:43 +08:00			`Multi: single`
docs/cmdline: change to .md for cmdline docs - switch all invidual files documenting command line options into .md, as the documentation is now markdown-looking. - made the parser treat 4-space indents as quotes - switch to building the curl.1 manpage using the "mainpage.idx" file, which lists the files to include to generate it, instead of using the previous page-footer/headers. Also, those files are now also .md ones, using the same format. I gave them underscore prefixes to make them sort separately: _NAME.md, _SYNOPSIS.md, _DESCRIPTION.md, _URL.md, _GLOBBING.md, _VARIABLES.md, _OUTPUT.md, _PROTOCOLS.md, _PROGRESS.md, _VERSION.md, _OPTIONS.md, _FILES.md, _ENVIRONMENT.md, _PROXYPREFIX.md, _EXITCODES.md, _BUGS.md, _AUTHORS.md, _WWW.md, _SEEALSO.md - updated test cases accordingly Closes #12751 2024-01-21 06:18:43 +08:00			`See-also:`
			`- ciphers`
			`Example:`
			`- --curves X25519 $URL`
tls: add CURLOPT_SSL_EC_CURVES and --curves Closes #5892 2020-08-29 20:09:24 +08:00			`---`
docs/cmdline: change to .md for cmdline docs - switch all invidual files documenting command line options into .md, as the documentation is now markdown-looking. - made the parser treat 4-space indents as quotes - switch to building the curl.1 manpage using the "mainpage.idx" file, which lists the files to include to generate it, instead of using the previous page-footer/headers. Also, those files are now also .md ones, using the same format. I gave them underscore prefixes to make them sort separately: _NAME.md, _SYNOPSIS.md, _DESCRIPTION.md, _URL.md, _GLOBBING.md, _VARIABLES.md, _OUTPUT.md, _PROTOCOLS.md, _PROGRESS.md, _VERSION.md, _OPTIONS.md, _FILES.md, _ENVIRONMENT.md, _PROXYPREFIX.md, _EXITCODES.md, _BUGS.md, _AUTHORS.md, _WWW.md, _SEEALSO.md - updated test cases accordingly Closes #12751 2024-01-21 06:18:43 +08:00
			# `--curves`

cmdline-opts: language cleanups Use imperative mood consistently for the first sentence describing an option. "Set this" instead "tell curl to set" or "this sets..." Plus some extra cleanups and rephrasing. Closes #13106 2024-03-12 17:34:58 +08:00			`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.
tls: add CURLOPT_SSL_EC_CURVES and --curves Closes #5892 2020-08-29 20:09:24 +08:00
			`--curves allows a OpenSSL powered curl to make SSL-connections with exactly`
docs: address proselint nits - avoid exclamation marks - use consistent number of spaces after periods: one - avoid clichés - avoid using 'very' Closes #8060 2021-11-26 15:46:59 +08:00			`the (EC) curve requested by the client, avoiding nontransparent client/server`
tls: add CURLOPT_SSL_EC_CURVES and --curves Closes #5892 2020-08-29 20:09:24 +08:00			`negotiations.`

cmdline-docs: use present tense, not future + some smaller cleanups Closes #11821 2023-09-08 20:32:29 +08:00			`If this option is set, the default curves list built into OpenSSL are ignored.`