On 01/16/2014 04:32 AM, Ben RUBSON wrote: > Issues 2.2 and 2.3, as well as reference [2] could be solved by using > random bytes. > How can this feature be enabled ?
Random bytes won't solve reference [2] because the same amount of random bytes (proportionally) will be added to each file, so you can still figure out the relative sizes of files in a directory, and the number of files in a directory. However, I think reference [2] is something that EncFS can't do much about, which is why I didn't explicitly mention it in the report. The leakage is inherent in the way it (and anything else like EncFS) works. The solution offered in [2] (appending a random amount of bytes) doesn't work, because there has to be an upper and lower bound on the amount of bytes added, and you can still compute a probability that a directory corresponds to something like a .torrent download of a music CD. Even just knowing how many files are in a directory leaks information. Using 16 random bytes (or 8 with Blowfish) can somewhat mitigate 2.3, since it is effectively randomizing the IV. However, it's not an ideal solution and I'm not sure if it really solves the problem. It definitely doesn't fix issue 2.2. Ciphertext past the first 64 byte chunk of the block only depends on the XOR of the random bytes with each other. There are only 256 possible values, so an adversary can just try them all. Anyway, to enable random bytes you have to create the filesystem in expert mode, and there's an option. I don't think you can add them to an existing filesystem. > > You say that as it is now, EncFS is not suitable for protecting > mission-critical data. > Then, just for information, what would you advise as a replacement ? > Full disk encryption (or TrueCrypt's file container) should be used whenever possible, since it avoids the leakage in reference [2]. If that doesn't fit the use case, there's eCryptfs, which might be better: http://ecryptfs.org/ I'm actually auditing ecryptfs next week so we'll see how good it is. Maybe someone else on the list knows of another alternative? -- Taylor Hornby ------------------------------------------------------------------------------ CenturyLink Cloud: The Leader in Enterprise Cloud Services. Learn Why More Businesses Are Choosing CenturyLink Cloud For Critical Workloads, Development Environments & Everything In Between. Get a Quote or Start a Free Trial Today. http://pubads.g.doubleclick.net/gampad/clk?id=119420431&iu=/4140/ostg.clktrk _______________________________________________ Encfs-users mailing list Encfs-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/encfs-users
