---
name: "gnutls_x509_privkey_get_key_id"
section: "3"
platform: "linux"
package: "gnutls"
version: "3.8.13-3"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/gnutls_x509_privkey_get_key_id"
---

# gnutls\_x509\_privkey\_get\_key\_id(3)

API function

## NAME

gnutls\_x509\_privkey\_get\_key\_id - API function

## SYNOPSIS

**#include \<gnutls/x509.h\>**

**int gnutls\_x509\_privkey\_get\_key\_id(gnutls\_x509\_privkey\_t** *key***, unsigned int** *flags***, unsigned char \*** *output\_data***, size\_t \*** *output\_data\_size***);**

## ARGUMENTS

- gnutls\_x509\_privkey\_t key

  a key

- unsigned int flags

  should be one of the flags from **gnutls\_keyid\_flags\_t**

- unsigned char \* output\_data

  will contain the key ID

- size\_t \* output\_data\_size

  holds the size of output\_data (and will be replaced by the actual size of parameters)

## DESCRIPTION

This function will return a unique ID that depends on the public key parameters. This ID can be used in checking whether a certificate corresponds to the given key.

If the buffer provided is not long enough to hold the output, then \* *output\_data\_size* is updated and **GNUTLS\_E\_SHORT\_MEMORY\_BUFFER** will be returned.  The output will normally be a SHA-1 hash output, which is 20 bytes.

## RETURNS

On success, **GNUTLS\_E\_SUCCESS** (0) is returned, otherwise a negative error value.

## REPORTING BUGS

Report bugs to \<bugs@gnutls.org\>.\
 Home page: https://www.gnutls.org

## COPYRIGHT

Copyright © 2001-2023 Free Software Foundation, Inc., and others.\
 Copying and distribution of this file, with or without modification, are permitted in any medium without royalty provided the copyright notice and this notice are preserved.

## SEE ALSO

The full documentation for **gnutls** is maintained as a Texinfo manual. If the /usr/share/doc/gnutls/ directory does not contain the HTML form visit

- https://www.gnutls.org/manual/