NAME

       CURLOPT_SSL_EC_CURVES - key exchange curves

SYNOPSIS

       #include <curl/curl.h>

       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_EC_CURVES, char *list);

DESCRIPTION

       Pass  a  string  as  parameter with a colon delimited list of Elliptic curve (EC) algorithms. This option
       defines the client's key exchange algorithms in the SSL handshake (if the SSL backend libcurl is built to
       use supports it).

       The application does not have to keep the string around after setting this option.

       Using this option multiple times makes the last set string override the previous ones. Set it to NULL  to
       restore back to internal default.

DEFAULT

       "", embedded in SSL backend

PROTOCOLS

       This functionality affects all TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc.

       This option works only with the following TLS backends: OpenSSL and wolfSSL

EXAMPLE

       int main(void)
       {
         CURL *curl = curl_easy_init();
         if(curl) {
           CURLcode res;
           curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
           curl_easy_setopt(curl, CURLOPT_SSL_EC_CURVES, "X25519:P-521");
           res = curl_easy_perform(curl);
           curl_easy_cleanup(curl);
         }
       }

AVAILABILITY

       Added in curl 7.73.0

RETURN VALUE

       curl_easy_setopt(3) returns a CURLcode indicating success or error.

       CURLE_OK (0) means everything was OK, non-zero means an error occurred, see libcurl-errors(3).

SEE ALSO

       CURLOPT_SSL_CIPHER_LIST(3), CURLOPT_SSL_OPTIONS(3), CURLOPT_TLS13_CIPHERS(3)

libcurl                                            2025-06-16                           CURLOPT_SSL_EC_CURVES(3)