CURLOPT_SS...ALGORITHMS(3) Library Functions Manual CURLOPT_SS...ALGORITHMS(3)
NAME
CURLOPT_SSL_SIGNATURE_ALGORITHMS - signature algorithms to use for TLS
SYNOPSIS
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_SIGNATURE_ALGORITHMS, char *list);
DESCRIPTION
Pass a char pointer, pointing to a null-terminated string holding the
list of signature algorithms to use for the TLS connection. The list
must be syntactically correct, it consists of one or more signature al-
gorithm strings separated by colons.
A valid example of a signature algorithms list with OpenSSL is:
"DSA+SHA256:rsa_pss_pss_sha256"
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 disable its use again.
Works with OpenSSL and its BoringSSL fork (added in 8.14.0).
DEFAULT
NULL, use built-in list
PROTOCOLS
This functionality affects all TLS based protocols: HTTPS, FTPS, IMAPS,
POP3S, SMTPS etc.
This option works only with the following TLS backends: OpenSSL
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_SIGNATURE_ALGORITHMS,
"DSA+SHA256:rsa_pss_pss_sha256");
res = curl_easy_perform(curl);
curl_easy_cleanup(curl);
}
}
HISTORY
OpenSSL support added in 8.14.0.
AVAILABILITY
Added in curl 8.14.0
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_SSLVERSION(3), CURLOPT_SSL_CIPHER_LIST(3), CUR-
LOPT_SSL_EC_CURVES(3), CURLOPT_USE_SSL(3)
libcurl 2026-07-12 CURLOPT_SS...ALGORITHMS(3)
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