private static byte[] scanPrivateKey(CryptobyConsole console) {
        byte[] retKey = null;
        do {
            scanner = new Scanner(System.in);
            String keyText = "";
            // Input Private Key for decryption
            System.out.println("\nEnter the private Key (Type '" + quit + "' to Escape):");
            try {
                while (!scanner.hasNext(CryptobyHelper.getEOBString())) {
                    if (scanner.hasNext(quit)) {
                        rsaCrypterText(console);
                    }
                    keyText = keyText + scanner.next();
                }
                retKey = CryptobyHelper.hexStringToBytes(keyText);
                keySize = retKey.length * 4;
            } // Catch false format of Input
            catch (NumberFormatException exp) {
                System.out.println("Not allowed Characters in Private Key! Just lower alphanumeric Characters!");
                retKey = BigInteger.ZERO.toByteArray();
                keySize = 0;
            } catch (NullPointerException exp) {
                System.out.println("NullPointerException catched! Try again!");
                retKey = BigInteger.ZERO.toByteArray();
                keySize = 0;
            }
        } while (keySize != 1024 && keySize != 2048 && keySize != 4096);
        return retKey;
    }