flag.Parse()

	if endpoint == "" {
		log.Fatalln("Endpoint is not provided")
	}

	if accessKey == "" {
		log.Fatalln("Access key is not provided")
	}

	if secretKey == "" {
		log.Fatalln("Secret key is not provided")
	}

	if bucket == "" && prefix != "" {
		log.Fatalln("--prefix is specified without --bucket.")
	}

	var minModTime time.Time

	flag.Parse()

	if sourceEndpoint == "" {
		log.Fatalln("source Endpoint is not provided")
	}

	if sourceAccessKey == "" {
		log.Fatalln("source Access key is not provided")
	}

	if sourceSecretKey == "" {
		log.Fatalln("source Secret key is not provided")
	}

	if sourceBucket == "" && sourcePrefix != "" {
		log.Fatalln("--source-prefix is specified without --source-bucket.")

	if *keyHex == "" {
		if b, err := os.ReadFile(*privKeyPath); err == nil {
			privateKey = b
			fmt.Println("Using private key from", *privKeyPath)
		}

		// Prompt for decryption key if no --key or --private-key are provided
		if len(privateKey) == 0 {
			reader := bufio.NewReader(os.Stdin)
			fmt.Print("Enter Decryption Key: ")

			text, _ := reader.ReadString('\n')
			// convert CRLF to LF