CURLOPT_SSL_EC_CURVES(3) Library Functions Manual CURLOPT_SSL_EC_CURVES(3)

CURLOPT_SSL_EC_CURVES - key exchange curves

#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_EC_CURVES, char *alg_list);

Pass a string as parameter with a colon delimited list of (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).

"", embedded in SSL backend

All TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc.

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

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);
  }
}

Added in 7.73.0. Supported by the OpenSSL backend.

Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.

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

2024-05-22 libcurl