SilcBool silc_pkcs_load_private_key(const char *filename,
                                        const unsigned char *passphrase,
                                        SilcUInt32 passphrase_len,
                                        SilcPrivateKey *ret_private_key);

    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, in case it is encrypted.