Garrett: PSA: upgrade your LUKS key derivation function

Matthew Garrett pointsout that many Linux systems using encrypted disks were installed with arelatively weak key derivation function that could make it relatively easyfor a well-resourced attacker to break the encryption:

So, in these days of attackers with access to a pile of GPUs, apurely computationally expensive KDF is just not a goodchoice. And, unfortunately, the subject of this story was almostcertainly using one of those. Ubuntu 18.04 used the LUKS1 headerformat, and the only KDF supported in this format is PBKDF2. Thisis not a memory expensive KDF, and so is vulnerable to GPU-basedattacks. But even so, systems using the LUKS2 header format used todefault to argon2i, again not a memory expensive KDF. New versionsdefault to argon2id, which is. You want to be using argon2id.

The article includes instructions on how to (carefully) switch an installedsystem to a more secure setup.