Hello hyamanieu,
well, we hope too, this will never ever happen!
In case of apocalypse you're fine if you have a copy of:
1. The Boxcryptor application
2. Your exported key from your account:
https://www.boxcryptor.com/en/help/boxcryptor-account/windows/#export-your-keys
Then, you will be able to work in "local mode" and decrypt your files.
Best regards,
Yasmin