public static function loadEncryptionKeyPair(string $filePath): EncryptionKeyPair
    {
        if (!\is_readable($filePath)) {
            throw new CannotPerformOperation(
                'Cannot read keyfile: '. $filePath
            );
        }
        return new EncryptionKeyPair(
            new EncryptionSecretKey(
                self::loadKeyFile($filePath)
            )
        );
    }