VERY LARGE main memories: cryptography

[John Gilmore]

[Net.arch has been discussing applications of very large main memories,
on the close order of a gigabyte.]

In article <22...@peora.UUCP>, jo...@peora.UUCP (Joel Upchurch) writes:
> One thing that no one has mentioned so far that you could do
> with very large memories is table lookups.

This is certainly a useful technique in cryptography. Someone wrote
a paper on how to break DES that involved writing many megabytes of stuff
on magtape so you could get it back quickly later when breaking an
encrypted message. Things would be a lot more tractable if the table
was in RAM instead.

Even a medium sized company or country could probably buy enough RAM
to decrypt DES quickly.
--
John Gilmore {sun,ptsfa,lll-crg,ihnp4}!hoptoad!gnu jgil...@lll-crg.arpa
May the Source be with you!

[David desJardins]

In article <10...@hoptoad.uucp> g...@hoptoad.uucp (John Gilmore) writes:
>This is certainly a useful technique in cryptography. Someone wrote
>a paper on how to break DES that involved writing many megabytes of stuff
>on magtape so you could get it back quickly later when breaking an
>encrypted message. Things would be a lot more tractable if the table
>was in RAM instead.
>
>Even a medium sized company or country could probably buy enough RAM
>to decrypt DES quickly.

While I'm not a big fan of DES, I don't think this is very accurate.
Unless there is some radically new method that no one outside NSA knows
about (I'm not ruling this out; it just seems that there is no sensible
way to discuss it), there is no way that a single-processor machine is
going to break DES in a reasonable period of time. And that is what
this discussion is about, large single-processor (or perhaps a few
processors, but not hundreds or thousands) machines with large amounts
of memory.

-- David desJardins