[tahoe-dev] Choice of tree-hash

[David-Sarah Hopwood]

On 24/09/12 20:35, David-Sarah Hopwood wrote:
> On 23/09/12 20:11, Tony Arcieri wrote:
>> 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.

... and also if there is an error in the computation of the hash, unless it is a
deterministic error producing the same wrong value when it was originally computed
and when it is checked.

-- 
David-Sarah Hopwood ⚥

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