[tahoe-dev] Choice of tree-hash

[David-Sarah Hopwood]

On 23/09/12 20:11, Tony Arcieri wrote:
> On Fri, Sep 21, 2012 at 5:02 AM, CodesInChaos <codesinchaos at gmail.com
> <mailto:codesinchaos at gmail.com>> wrote:
> 
>     This hash doesn't only detect bugs. It identifies the file. So you can
>     easily see that a file stored on tahoe is the same one as a file
>     stored on cryptosphere. (Obviously assuming knownledge of read caps)
> 
> Why not use a hash (tree) of the ciphertext for this purpose? I suppose encrypting the
> hash of the plaintext accomplishes the same thing...

In addition to CodesInChaos' reply:

Integrity checking using a hash of the ciphertext relies on the decryption being
correct. Checking using an encrypted hash of the plaintext does not: the check will
fail if there is an error in either the decryption of the encrypted-hash, or the
decryption of the ciphertext.

If the plaintext hash were standardized, it could potentially also be sent as an
HTTP header and checked by the web browser, giving better end-to-end integrity.

-- 
David-Sarah Hopwood ⚥

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