Solving "Wrong Auth Protocol Attempted" Error in PuTTY X11 Proxy

PuTTY X11 Proxy is a software application used to tunnel SSH connections. But sometimes, the user can encounter an error saying "wrong authentication protocol attempted". If you're encountering this error and don't know how to solve it, this guide will help you.

Error Message

When an X11 session is established via PuTTY, the X11 encryption and rights settings are normally set as default. But if any incorrect settings are used, PuTTY will throw this error message:

“wrong authentication protocol attempted”

Instructions on How to Fix

There are various settings you can use to fix wrong authentication protocol attempted error in PuTTY X11 Proxy. You need to follow this step-by-step process to fix the issue.

  1. Open PuTTY and login to the remote machine using SSH.
  2. After logging in, run the command xauth
  3. If the output of the xauth command doesn't include MIT-MAGIC-COOKIE-1, run the command xauth -q to find out where it’s coming from.
  4. Find out the .Xauthority file associated with your username and open it.
  5. In the .Xauthority file, look for the line containing MIT-MAGIC-COOKIE-1 and delete the line.
  6. Update the .Xauthority file with the new value.
  7. Finally, refresh the window and try the connection again.

You should now be able to log on successfully with the right authentication protocol.


Q1. What is the PuTTY X11 Proxy?

A1. PuTTY X11 Proxy is a software application that enables users to tunnel SSH connections. It enables users to establish an X11 session over the SSH connection.

Q2. What is the "wrong authentication protocol attempted" error?

A2. This error is thrown by PuTTY when the wrong authentication protocol settings are used. This error can be solved by resetting the authentication protocol settings.

Q3. How can I reset the X11 authentication protocol settings?

A3. There are various settings you can use to reset X11 authentication protocol settings. You need to login to the remote machine and manipulate the contents of the .Xauthority file.

A4. The MIT-MAGIC-COOKIE-1 setting is an X11 encryption and rights setting. It is used to authenticate an X11 connection and must be set correctly for the connection to be established.

A5. If the MIT-MAGIC-COOKIE-1 setting is not found in the .Xauthority file, you can run the command xauth -q to find out where it’s coming from. Then, you can update the file with the new value.

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