Lukas, the error was the same in version 2018r4, so, there is NOT any problem with 2019R3.
But, if I utilize the following code, the Windows is "forced" to ask for permission :
Dim cert2pss As System.Security.Cryptography.X509Certificates.X509Certificate2 = Signer
Dim pfx As Byte() = cert2pss.Export(System.Security.Cryptography.X509Certificates.X509ContentType.Pfx, "David")
Signer = Certificate.LoadPfx(pfx, "David", KeySetOptions.PreferCng Or KeySetOptions.Exportable)
But interestingly I have 2 scenarios:
- If just signing the message, Outlook shows me 100% signed but RSA/SHA256.
- If signing and encrypting the message (in this order), Outlook shows me RSASSA-PSS /SHA256 but also reports "an error" like "the message can be altered". The error is only in the SIGN layer, the encryption layer appears 100%.
If you want, I can send an image to you.