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5.1 Abstract key types

Since there are many forms of a public or private keys supported by GnuTLS such as X.509, PKCS #11 or TPM it is desirable to allow common operations on them. For these reasons the abstract gnutls_privkey_t and gnutls_pubkey_t were introduced in gnutls/abstract.h header. Those types are initialized using a specific type of key and then can be used to perform operations in an abstract way. For example in order to sign an X.509 certificate with a key that resides in a token the following steps can be used.

#inlude <gnutls/abstract.h>

void sign_cert( gnutls_x509_crt_t to_be_signed)
{
gnutls_x509_crt_t ca_cert;
gnutls_privkey_t abs_key;

  /* initialize the abstract key */
  gnutls_privkey_init(&abs_key);

  /* keys stored in tokens are identified by URLs */
  gnutls_privkey_import_url(abs_key, key_url);

  gnutls_x509_crt_init(&ca_cert);
  gnutls_x509_crt_import_url(&ca_cert, cert_url);

  /* sign the certificate to be signed */
  gnutls_x509_crt_privkey_sign(to_be_signed, ca_cert, abs_key, 
                               GNUTLS_DIG_SHA256, 0);
}