[tahoe-dev] proposal: add padding

[Tony Arcieri]

On Fri, Jul 12, 2013 at 2:37 AM, Iraklis . <leontiad at gmail.com> wrote:

>  You are missing the following:
> Files are encrypted for deduplication. That implies a way to derive a key
> from the content of the files. That is if two files are similar they will
> have similar ciphertexts
>

No, because they are encrypted under a key derived by a hash function, and
one property of a secure hash function is that similar content produces
completely different hashes, even if you just change one bit.

Using this content hash to seed a PRNG (and derive encryption keys for the
content) will produce completely different pseudorandom padding, even for
similar files.

-- 
Tony Arcieri
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://tahoe-lafs.org/pipermail/tahoe-dev/attachments/20130712/0a233f27/attachment.html>