[tahoe-dev] proposal: add padding

[Iraklis .]

Sorry when i said similar i meant equivalent i didn't assume content 
based hashing with a similarity threshold, etc...

Regards,

Iraklis
On 07/12/2013 05:57 PM, Tony Arcieri wrote:
> On Fri, Jul 12, 2013 at 2:37 AM, Iraklis . <leontiad at gmail.com 
> <mailto: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
>
>
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