Remote Desktop: An authentication error has occurred. – This could be due to CredSSP encryption oracle remediation.

Hi everyone,

I ran into an auth issue with remote desktop today:

An authentication error has occurred.
The function requested is not supported.
Remote computer: XXXX

This could be due to CredSSP encryption oracle remediation.
For more information, see hhtps://go.microsoft.com/fwlink/?linkid=866660

The solution is to add the May 2018 Windows Security Update on both the remote and local machines. If that’s not possible a registry entry can be added to the local machine to circumvent the issue. This can be done by running the following command in a command prompt as administrator:

REG ADD HKLM\Software\Microsoft\Windows\CurrentVersion\Policies\System\CredSSP\Parameters\ /v AllowEncryptionOracle /t REG_DWORD /d 2

You can also add the entry manually via regedit.

The cause is actually because of a security update in windows. If either the remote or local machine has the update and the other does not the error is triggered. There’s more info available on the following page: https://github.com/stascorp/rdpwrap/issues/480

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