6 ms·
De-dupe: Wuala encrypts the file with a key derived from the file itself. This key is then encrypted with the user's key and both (the file and the encrypted ke
by gst 15y ago
De-dupe: Wuala encrypts the file with a key derived from the file itself. This key is then encrypted with the user's key and both (the file and the encrypted key) are uploaded to the cloud. Disadvantage: If the file is known to an attacker (i.e., a copyright holder) the attacker can possibly find out which users have access to this file. Advantage: Allows for de-duplication, but is more secure than Dropbox.
Block-level updates: I don't see a problem with this. Partition the file into blocks on the client (before the encryption). The server doesn't need access to the data for this.
- tptacek 15y agoAs Steve Weis pointed out in an earlier thread about schemes like this, deriving keys from the contents of files breaks semantic security. Lay engineers reason about this problem the way you just did: "the RIAA can tell I have Lady Gaga MP3s". But practitioners are worried about much more subtle and devastating flaws, particularly in cases where attackers may exercise some control over the blocks being encrypted. Any scheme that derives passwords from file contents gives me the willies.
- drivebyacct2 15y agoMost file-level encryption that I'm aware destroys benefits of blocked data. For example, changing a few bytes in an encrypted file will cause MANY bytes to change in the actual file on the disk... at least with ecryptfs and truecrypt. If there is an encryption scheme that works well with striping, I'd really super appreciate you pointing me in that direction - it would greatly help with a problem I'm currently trying to solve.