On Mon, Oct 05, 2020 at 07:36:03AM +0000, Satya Tangirala wrote: > This patch series adds support for metadata encryption to F2FS using > blk-crypto. This patch series needs more explanation about what "metadata encryption" is, why people will want to use it (as opposed to either not using it, or using fscrypt + dm-crypt instead), and why this is the best implementation of it. > Patch 2 introduces some functions to fscrypt that help filesystems perform > metadata encryption. Any filesystem that wants to use metadata encryption > can call fscrypt_setup_metadata_encryption() with the super_block of the > filesystem, the encryption algorithm and the descriptor of the encryption > key. The descriptor is looked up in the logon keyring of the current > session with "fscrypt:" as the prefix of the descriptor. I notice this is missing the step I suggested to include the metadata encryption key in the HKDF application-specific info string when deriving subkeys from the fscrypt master keys. The same effect could also be achieved by adding an additional level to the key hierarchy: each HKDF key would be derived from a fscrypt master key and the metadata encryption key. We need one of those, to guarantee that the file contents encryption is at least as strong as the "metadata encryption". - Eric
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