optional password used to decrypt PKCS12 file, bags and keys.
DESCRIPTION
This function sets a certificate/private key pair and/or a CRL in
the gnutls_certificate_credentials_t structure. This function may
be called more than once (in case multiple keys/certificates exist
for the server).
MAC
ed PKCS12 files are supported. Encrypted PKCS12 bags are
supported. Encrypted PKCS8 private keys are supported. However,
only password based security, and the same password for all
operations, are supported.
The private keys may be RSA PKCS1 or DSA private keys encoded in
the OpenSSL way.
PKCS12 file may contain many keys and/or certificates, and there
is no way to identify which key/certificate pair you want. You
should make sure the PKCS12 file only contain one key/certificate
pair and/or one CRL.
It is believed that the limitations of this function is acceptable
for most usage, and that any more flexibility would introduce
complexity that would make it harder to use this functionality at
all.