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ZFS encryption works in a similar fashion, and ext4 also has encryption (which is used by default in Android). Personally I'm not a huge fan of this because un
by cyphar 8y ago
ZFS encryption works in a similar fashion, and ext4 also has encryption (which is used by default in Android).
Personally I'm not a huge fan of this because unlike the clear benefits of giving filesystems control over raw devices, full disk encryption has requirements that can't really be provided partially. You want to ensure no metadata about the filesystem structure or files will be known without knowing the encryption key but this is clearly not possible without having block device layer encryption. ZFS encryption allows for all sorts of useful operations on encrypted filesystems without having the key. This is cool, but also obviously provides a lot of information about the filesystem structure. Also dedup tables aren't encrypted in this setup. ext4 only encrypts filenames and contents, which is worse in some respects.
- exikyut 8y ago> Also dedup tables aren't encrypted in this setup. This sounds like low-hanging fruit for a security researcher to try their hand at: comprehend the dedupe table format, and see what you can derive from it (basically the real-world version of https://xkcd.com/704/ https://xkcd.com/704/).
- koverstreet 8y agoThe only metadata stored in the clear in bcachefs is the superblock and the very first part of the btree node and journal entry headers - just the checksum, magic number (identifying it as a btree node/journal header), and a flags field which mainly contains the checksum/encryption type. So an attacker can tell roughly how much metadata you have, but literally nothing about the contents.