When validating the signature of a digitally signed xml, if you get an error message saying "Access is denied", the issue may be related to corrupted permissions on a Windows system.
To resolve this corruption, restore the permissions of the c:\Users\All Users\Application Data\Microsoft\Crypto\RSA\MachineKeys folder by following the procedure in this Microsoft article.
You can also restore the permissions by running the QlmDiagnostics.exe tool attached to this article. To use the QlmDiagnostics.exe tool:
- Download the zip file and extract it
- Open a command prompt as Administator (Run As Administrator)
- Type: QlmDiagnostics.exe /rsa