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CURLOPT_TLS13_CIPHERS - specify ciphers suites to use for TLS 1.3 #include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_TLS13_CIPHERS, char *list); Pass a char *, pointing to a null-terminated string holding the list of cipher suites to use for the TLS 1.3 connection. The list must be syntactically correct, it consists of one or more cipher suite strings separated by colons. You'll find more details about cipher lists on this URL: https://curl.haxx.se/docs/ssl-ciphers.html This option is currently used only when curl is built to use OpenSSL 1.1.1 or later. If you are using a different SSL backend you can try setting TLS 1.3 cipher suites by using the CURLOPT_SSL_CIPHER_LIST option. The application does not have to keep the string around after setting this option. NULL, use internal default All TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc.

CURL *curl = curl_easy_init();
if(curl) {
 curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
 curl_easy_setopt(curl, CURLOPT_TLS13_CIPHERS,
 "TLS13-CHACHA20-POLY1305-SHA256");
 ret = curl_easy_perform(curl);
 curl_easy_cleanup(curl);
}

Added in 7.61.0. Available when built with OpenSSL >= 1.1.1. Returns CURLE_OK if supported, CURLE_NOT_BUILT_IN otherwise. CURLOPT_SSL_CIPHER_LIST "(3), " CURLOPT_SSLVERSION "(3), " CURLOPT_PROXY_SSL_CIPHER_LIST "(3), " CURLOPT_PROXY_TLS13_CIPHERS "(3), " CURLOPT_PROXY_SSLVERSION "(3), " CURLOPT_USE_SSL "(3), "