Nth digit of PI

[Tim Dixon]

On 16 Jun 2000 17:36:32 GMT, israel at math.ubc.ca (Robert Israel) wrote:

>In article <394a5ed7.83928743 at 10.1.1.28>,
>Tim Dixon <tdixon.no at spam.fwi.com> wrote:
>>On Fri, 16 Jun 2000 16:33:59 GMT, Courageous <jkraska1 at san.rr.com>
>>wrote:
>
>
>>>> Suppose, however, that you could get digit 'n' of pi directly (or e,
>>>> or any other inifinte, nonrepeating sequence).  All I have to do is
>>>> communicate which digit of pi the message key starts at, and I can
>>>> generate the rest of the key.
>>>
>>>This is a collosally bad idea, IMO.
>
>>Just for curiosity, why?
>
>Because the real key is the number of the digit that you start at, and
>that's pitifully small by cryptographic standards.  The time to generate
>the n'th digit is not much less than the time to generate all the digits
>up to the n'th, given that you have lots of memory available.  So the
>cryptanalyst with a computer somewhat bigger than yours could try all
>the keys you could be using.  
>

Right, but in the hypothetical example where I can get *any* digit of
pi, that could be any of an infinite number of starting points.
>Robert Israel                                israel at math.ubc.ca
>Department of Mathematics        http://www.math.ubc.ca/~israel 
>University of British Columbia            
>Vancouver, BC, Canada V6T 1Z2