NOTE: Since this was written in 2018 cryptsetup-reencrypt appeared which should be used instead of luksipc, although it works on the same principle - downsizing partition and using free space to re-encrypt

Have the disk encrypted with a keyfile. Delete the keyfile.

There is simply no way to securely erase them because of the way the wear leveling works. Even if it appears you wiped a sector it may just be written to another sector. You’d have to run the following over the whole disk to get close to a 100% erasure dd if=/dev/urandom of=/dev/xxx but this will take a while and will reduce the ssd’s usable life quite a bit

https://www.digitalocean.com/community/tutorials/an-introduction-to-securing-your-linux-vps https://www.digitalocean.com/community/tags/security?type=tutorials

PGP allows you to encrypt data using multiple keys, but any key there will be able to decrypt the data. What if you want to encrypt your data so that ALL keys are required to decrypt the data? For this you can chain encryption. Here is an example on how to chain three AES256 keys.