[ExI] The second step towards immortality

[Martin Sustrik]

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On 02/01/14 21:52, Adrian Tymes wrote:
> On Jan 2, 2014 12:22 PM, "Martin Sustrik" <sustrik at 250bpm.com>
> wrote:
>> That's the point of homomorphic encryption. Take homomorphic 
>> multiplication: E(a.b) = E(a).E(b)
> 
> Right, but you also have D(E(a.b)) = a.b, since at some point you
> have to write the correct bitcoin transaction message out.  Once
> the emulator finds this, and has E(a), it can do D(E(a)) = a.

AFAIU, what you get by such observation is some number of
plaintext-cyphertext pairs (not of your choosing).

This sounds to be much weaker attack than either chosen plaintext
attack or chosen cyphertext attack, which can both be beaten by a
correctly chosen modern cypher. Anyway, rigorous cryptographical
analysis would be needed to prove the point.

Martin
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