full-disclosure - Re; Time Expiry Algorithm

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Message-ID: <73E117E4-3C18-11D9-A0C0-000D93C0F38C@teknovis.com>
From: andfarm at teknovis.com (Andrew Farmer)
Subject: Re; Time Expiry Algorithm

On 21 Nov 2004, at 00:14, Jacqueline Singh wrote:
> Gautam R. Singh <gautam.singh@...il.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.)
>
> What if you decided to code into the encryption the use of atomic
> clocks, and include more than one or two as a redundancy/security
> check?

That's an implementation, not an algorithm.

An encryption *algorithm* must be a fixed set of rules that map inputs 
to outputs. In your proposed algorithm, one of the inputs is the 
current time - and that can be changed, by the *definition* of an 
algorithm.
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