Re: Comparing Cryptographic Key Sizes

[David Lucas <davidlu@sco.COM>]

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At 09:52 24/06/97 -6, Peter Trei <trei@process.com> wrote:
>Adam Back <aba@dcs.ex.ac.uk> writes.

<...>

>> About 10 years ago now Michael Wiener made a design for such a DES
>> breaking machine.  He estimated it would cost $10,000,000 to build 
a
>> machine which would break a 56 bit DES encrypted message a few 
hours.
>> His machine was scalable, pay more money, break the key faster, 
pay
>> less take longer.  The estimate was that could build one with 
enough
>> DES key searching units to break it in a day for $1,000,000.  That 
was
>> 10 years ago.  10 years is a long time in the computer industry.
>> Nowadays you build the machine more cheaply as chip technology has
>> progressed, and computers are much faster per $.  Estimates are 
around
>> $100,000 to build the machine (neglecting hardware engineers
>> consultancy fees).
>
>Go back and check the numbers - if you don't the journalists will. 
>(I don't have this paper to hand either :-( ) The Wiener paper is 
>much more recent (93?) , and the cost much lower (I think it was 
>about $1M for HW and $500K for development costs, for a 3.5 hour 
>machine).

Relevant section of AC2 is Table 7.1 (page 153)

The numbers referred to above are slightly out:

In 1995, $1M would give you a machine that would break 56-bit DES in 
an average of 3.5 hours

A $10M machine would break 56-bit DES in an average of 21 minutes

[Double the times for an exhaustive keysearch]

<...>
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
               David Lucas - Test Engineer @ SCO Cambridge.
                          E-mail: davidlu@sco.com

 Opinions expressed within this message are my own and do not necessarily
            represent those of my employer * I am not a lawyer
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