I think it is better to check this in one task instead of different tasks for encrypt and decrypt / verify
At the moment we have a green background for the results of a decryption and/or verification, if it was successful.
This does not work with high contrast mode.
And in case of GnuPG VSD a compliant signature looks the same as a not compliant one if you only go by the color and do not read the text.
Should you decide on only a colored icon / bar / whatever please keep in mind that a different color/shade for "valid but not VS-NfD compliant" would be good.
In high contrast mode the background should always be white or black.
Because color is a bad status indicator with regard to accessibility, we should think about using an icon as status indicator (additionally to color).