Windows : RDP An authentication error has occurred. The function requested is not supported

By | May 13, 2018

Since the latest Windows Updates, you might be encountering the following error when you RDP to another computer or server :

An authentication error has occurred.
The function requested is not supported

Remote computer:
This could be due to CredSSP encryption oracle remediation.
For more information, see https://goomicrosoft.com/fwlink/?linkid=866660

This is basically due to the fact that your client machine have latest updates installed and the remote computer or server does not. Your client refuse to connect because the target computer use weaker settings.

The right solution, in an ideal world would be updating the remote machine with latest updates, but it is not always possible in the immediate or you might need to actually be able to connect to it to do so!

You can workaround this issue by modifying the settings in the registry of your client machine as followed :

NOTE : The following steps can be easily achieved running the HotFix registry script provided below. It should be executed with the administrative privileges (right click, Run as administrator). Right click on the link, and then “save as”. Your security software might complain about downloading a “.reg” file and are totally right about it! Those scripts should be run only if you trust the issuer.

https://www.itechlounge.net/ITechHotFix/ITechHotFix-RDP-CredSSP-10052018.reg

Else, here are the steps to do the same thing below :

1. Open the registry editor :

2. Browse to the following :

HKEY_LOCAL_MACHINE \ SOFTWARE \ Microsoft \ Windows \ CurrentVersion \ Policies \ System

3. Create the following keys :

CredSSP \ Parameters

4. Add the following DWORD (32-bit) value :

And set the value to :

5. Reboot your computer, you should be able to connect once rebooted. Please remember to remove that fix once all your remote computers are updated.

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