Couldn't reproduce it.

When I set it to Yes, the existing data in the DB is saved and encrypted. When I set it to No, the existing data in the DB is saved and decrypted.
Just in case, I tried it in German too, without problem.

The problem was caused by having copied CPDB tables directly from 3.x to 5.x. That caused DB updates to not be executed.
The fix was to execute these updates manually:
UPDATE lime_participant_attribute_names SET core_attribute='N';
UPDATE lime_participant_attribute_names SET encrypted='N';

Thanks @gabrieljenik for the great help. This ticket can be closed.

I am not sure those are included in the update scrtips.
Anyway, the code doesn't consider blank to be a N when reading if an attribute is encrypted or not.

Then, when asking to encrypt, the data was not encrypted but still the attribute marked as encrypted.
Then wen trying to decrypt, the decryption failed.

Another problem, when failed, it failed silently, as the exception was not shown, neither frienly error informed.

There are issues. Still, de-assigning myself from it as to allow priorization from @tibor.pacalat
Thanks

Master: https://github.com/LimeSurvey/LimeSurvey/pull/3670
v5: https://github.com/LimeSurvey/LimeSurvey/pull/3671

During the update from 3 to 5, the “encrypted” and “core_attribute” fields of the existing attributes are not set.

So in this part the variables do not have “N”, but ““ (see attachment)

We updated the code so that it does not check “N” but !=”Y”. Maybe even add isEncrypted and isCoreAttribute methods to the model.

@tibor.pacalat: This is very sensistive as it involves encryption.

We updated the code so that it does not check “N” but !=”Y”. Maybe even add isEncrypted and isCoreAttribute methods to the model.

I'm OK with this solution.

What for token and response ? We check != 'N' or == 'Y' ?

Tested and merged.

Fix committed to 5.x branch: http://bugs.limesurvey.org/plugin.php?page=Source/view&id=35969

Fix committed to 5.x branch: http://bugs.limesurvey.org/plugin.php?page=Source/view&id=35968

Fixed in Release 6.4.3+240122

Fixed in Release 5.6.52+240123