mailing list archives
Re: Re; Time Expiry Algorithm
From: Raj Mathur <raju () linux-delhi org>
Date: Sun, 21 Nov 2004 21:10:45 +0530
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"jax" == Jacqueline Singh <jacqueline.singh () gmail com> writes:
jax> /me shakes her head at Andrew Farmer. Okay, now it's just
jax> ridiculous to suggest that you wouldn't be able to implement
jax> a time limitation on something encrypted simply because
jax> "clocks can be changed".
jax> What 'clocks' are talking about -- which are you basing it
jax> off of?
jax> What if you decided to code into the encryption the use of
jax> atomic clocks, and include more than one or two as a
jax> redundancy/security check?
jax> Someone's really going create a huge conspiracy to change a
jax> few of the world's atomic clocks drastically to be able to
jax> crack someone's encrypted data? :P
Nope, but one would happily set a policy that re-routed requests to
the atomic clocks to a local system, also with flawed time, in an
intermediate router. There is no way to have time-limited encryption,
even under control of a remote server, since the first time the
document is decrypted and rendered the client just needs to save the
Remember Apple's Fairplay and Hymn? Similar problem -- once the
decrypted data stream is available on the local PC there's no way to
prevent the user from saving it in a format of her choice; unless you
make a blackbox appliance, which too would get cracked eventually.
- -- Raju
>> To: "Gautam R. Singh" <gautam.singh () gmail com> Cc:
>> Full-Disclosure Full-Disclosure
>> <full-disclosure () lists netsys com> From: Andrew Farmer
>> <andfarm () teknovis com> Subject: Re: [Full-disclosure] Time
>> Expiry Alogorithm?? Date: Fri, 19 Nov 2004 10:28:20 -0800
jax> Gautam R. Singh <gautam.singh () gmail com> wrote:
>> I was just wondering is there any encrytpion alogortim which
>> expires with time. For example an email message maybe
>> decrypted withing 48 hours of its delivery otherwise it become
>> usless or cant be decrypted with the orignal key
>>> No. Think about it for a moment.
>>> (Clocks can be changed.)
Raj Mathur raju () kandalaya org http://kandalaya.org/
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It is the mind that moves
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