RDP OTP (Remote Desktop Protocol)

How does it work?

Everytime you log into your remote desktop environment, your password gets automatically changed. The new password is then encrypted with the public key of a personal RSA key pair. The key pair's only purpose is to be used to send one time passwords with an extra level of safety. Your encrypted password is then encoded as an QR code image. This QR code is uploaded to any FTP, WebDAV or network share of your choice. Then you can access the QR code image with the browser even from untrusted systems. Your smartphone holds the private key of your RSA key pair. It is therefor able to decrypt your one time password from the scanned QR code image. You can read the unencrypted password from the screen of your smartphone and use it to log into your remote desktop environment using the untrusted system. Now that you are logged in, the password has already been changed in the background.

Installation procedure

Install

https://play.google.com/store/apps/details?id=de.sbeh.rdp_otp&hl=en

onto your android device

Run app RDP OTP on your android device

Click Generate key which generates a RSA 1024 bit keypair

Private key is only accessable by this app

Public key is saved as pubkey.pem on the external sd card

Copy pubkey.pem to your remote desktop session

In your remote desktop session, copy

https://github.com/sbeh/RDP-OTP/raw/master/Windows/RDP%20OTP%20Server/bin/Debug/RDP%20OTP%20Server.exe

to a folder or your choice

Place the pubkey.pem in the same folder

Create a file oldPass.txt in the same folder, which contains your current password

No line breaks please!

Make it accessable only by you

Create a file uploadTo.url in the same folder, that contains a link where the QR code is going to be uploaded to. It should look similar to one of these:

file://N:/Storage/OTP_of_DevMachine.png

ftp://username:P4$$w0rd@cloudspace.mycompany.net/myPersonalSpace/LoginMeIn.png

https://ralf:ralfspassword@webdavhost.intern/OTP.png

file://C:/Users/User/Dropbox/PublicSecrets/MyLogin.png

No line breaks please!

Place a shortcut to RDP OTP Server.exe in

C:\Users[Your user name]\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup

to ensure that your password gets changed every time you log in