bool silc_pkcs_load_private_key(const char *filename,
                                    SilcPrivateKey *private_key,
                                    unsigned char *passphrase,
                                    SilcUInt32 passphrase_len,
                                    SilcUInt32 encoding);

    Loads private key from file and allocates new private key.  Returns TRUE
    if loading was successful.  The `passphrase' is used as decryption
    key of the private key file.