OpenZFS
2 HN recommenders · recommended in 5 months, 2016–2022
49:43 · 14K views · Oct 10, 2016
Tom Caputi presents the design of native encryption for ZFS at the OpenZFS Developer Summit, including design decisions and how authentication uses checksum fields.
Recommended whenever ZFS encryption comes up as the authoritative explanation of how it was added and its trade-offs at scale.
5 comments from Hacker News
On the contrary, it makes it suitable for file systems! File systems are not block devices, they are data structures on top of block devices — it's the job of these data structures to keep stuff, such as data, inodes, and... keys, and IVs, and MACs, checksums, etc. TFS uses Speck in XEX mode (edit: I just realized you're the author, so you already know that :). tptacek wrote a nice post about it: [LINK] and I quote: "If you’re encrypting a filesystem and not disk blocks, still don’t use XTS! Filesystems have format-awareness and flexibility. Filesystems can do a much better job of encrypting a disk than simulated hardware encryption can." Edit: check out this presentation on how encryption was bolted on ZFS: this video (slides: [LINK] ) It's not perfect, but it provides data authentication by reusing checksum fields for storing MACs. Edit 2: also check out bcachefs encryption design doc: [LINK] (also not perfect, but uses proper AEAD — ChaCha20-Poly1305. I sent some questions and suggestions to the author, but received no reply :/)
The problem is that a stream cipher is going to have some per-object uniqueness (a salt, IV, etc.), so by design even if you feed it related input blocks you will get different output blocks. This is, of course, antithetical to deduplication: so you need to check/store the hash of the input before it goes through the cipher. The presentation about ZFS' native encryption[1] covers many of these sorts of trade-offs necessary to do full-disk encryption at scale. [1]: this video
Native ZFS encryption may become available soon. It is pending code review: [LINK] There was a presentation of this by Tom Caputi at the most recent OpenZFS Developer Summit. Slides: [LINK] Video: this video Conference: [LINK]
I work with Tom at Datto. He presented all of his design decisions at the OpenZFS developer conference here: [LINK] Slides: [LINK] Video: this video
This is still geli+zfs, and not native zfs encryption that was recently presented in OpenZFS Developer Summit [0]. [0] this video