Re: Timed-release crypto and information economics

[tcmay@got.net (Timothy C. May)]

At 6:52 PM 11/9/95, Beavis B. Thoopit wrote:
>> That's a pretty large number of assumptions:
>>
>>       tamper-proof delay line
>>       => tamper-proof crypto box ("transformation function with state")
>>       => tamper-proof delay line
>>
>> Why not just put a tamper-proof clock in the tamper-proof crypto box
>> and not bother with the delay lines?
>
>The tamper proof aspect is really secondary to the math question.
>The idea that if I set up a stream of bits through a transform, that
>the original state of the transform affects the final outcome after
>N iterations.

The tamper-proof (more correctly, "tamper-resistant" or
"tamper-responding") hardware is so that attackers do not alter the clocks,
as one example, to "speed up" the time release. Or grab the key, as another
example.

(Cranking up the clock speed may or may not be possible and still have the
device work, but it's still an attack to consider.)

If the attacker can grab the internal state of the device, he can of course
run the "transform" talked about above on his equipment.

>If the transform exists, it will ease/eliminate the reliance on the
>"economics" of cryptography to build a tamper-proof physical device.

You'll need to more carefully argue your thesis. I cannot imagine a method,
save perhaps for quantum computing techniques, which can avoid the need for
"secure secrets," either via a person keeping a secret or a box keeping a
secret.

If the box is not secure against tampering, and an attacker gets in, he
effectively "knows" all of the secrets.

BTW, the "launch into solar orbit" scheme that has again surfaced here is
just a variant of making the costs of an attack very high.

--Tim May

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