CURLOPT_HTTPSIG_ALGORITHM(3) Library Functions Manual
NAME
CURLOPT_HTTPSIG_ALGORITHM - RFC 9421 HTTP Message Signatures algorithm
SYNOPSIS
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HTTPSIG_ALGORITHM,
long algorithm);
DESCRIPTION
This feature is experimental and may change before it is considered
stable. We advise against using it in production.
Enable RFC 9421 HTTP Message Signatures on outgoing requests. Pass a
long set to one of the values below to select the signing algorithm.
CURLHTTPSIG_NONE (0)
Disable HTTP Message Signatures.
CURLHTTPSIG_ED25519 (1)
Sign with Ed25519 (RFC 8032). Requires a TLS backend with
Ed25519 support.
CURLHTTPSIG_HMAC_SHA256 (2)
Sign with HMAC-SHA256.
Setting this option to a non-zero value also sets CURLOPT_HTTPAUTH(3)
to CURLAUTH_HTTPSIG. The options CURLOPT_HTTPSIG_KEY(3) and
CURLOPT_HTTPSIG_KEYID(3) must also be set.
DEFAULT
CURLHTTPSIG_NONE (0)
PROTOCOLS
This functionality affects http only
EXAMPLE
int main(void)
{
CURL *curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/api");
curl_easy_setopt(curl, CURLOPT_HTTPSIG_ALGORITHM, CURLHTTPSIG_ED25519);
curl_easy_setopt(curl, CURLOPT_HTTPSIG_KEY,
"9f8362f87a484a954e6e740c5b4c0e84"
"229139a20aa8ab56ff66586f6a7d29c5");
curl_easy_setopt(curl, CURLOPT_HTTPSIG_KEYID, "my-key-id");
curl_easy_perform(curl);
}
}
AVAILABILITY
Added in curl 8.22.0
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_HTTPAUTH(3), CURLOPT_HTTPSIG_HEADERS(3),
CURLOPT_HTTPSIG_KEY(3), CURLOPT_HTTPSIG_KEYID(3)
libcurl 2026-09-03 CURLOPT_HTTPSIG_ALGORITHM(3)
curl 8.22.0 - Generated Sun Sep 6 12:43:48 CDT 2026