3 ms·

I continue to not understand how people imagine these services working (de-dupe, block level updates, etc) without access to the unsecured version of the data.

I continue to not understand how people imagine these services working (de-dupe, block level updates, etc) without access to the unsecured version of the data. As for the claims about what Amazon could do to your data... there's even less sinister options. S3 is not 100% safe storage. There's a chance for bit rot and that may occur. If you don't check the file yourself, you won't know. Again, that seems a bit inevitable, no? edit: left out a 'not'

cperciva 15y ago
There's a sucker born every minute. Jungle Disk claims to be secure, and most people believe them -- most people have no way to assess whether they're doing things right or not.
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 ago
  As 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 ago
  Most 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.

cperciva 15y ago

There's a sucker born every minute. Jungle Disk claims to be secure, and most people believe them -- most people have no way to assess whether they're doing things right or not.

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 ago
As 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 ago
Most 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.