CURLOPT_HTTPSIG_KEYID(3)   Library Functions Manual   CURLOPT_HTTPSIG_KEYID(3)

NAME
       CURLOPT_HTTPSIG_KEYID - key identifier for HTTP Message Signatures

SYNOPSIS
       #include <curl/curl.h>

       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HTTPSIG_KEYID, char *keyid);

DESCRIPTION
       This feature is experimental and may change before it is considered
       stable. We advise against using it in production.

       Pass a null-terminated string that identifies the key used for RFC 9421
       HTTP Message Signatures. This value is included as the keyid parameter
       in the Signature-Input header, allowing the server to look up the
       corresponding verification key.

       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.

DEFAULT
       NULL

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_HTTPSIG_ALGORITHM(3), CURLOPT_HTTPSIG_KEY(3)

libcurl                           2026-09-02          CURLOPT_HTTPSIG_KEYID(3)