From: "Ian Farquhar" <ianf@sydney.sgi.com>
Date: Wed, 28 Dec 94 14:10:49 PST
To: cypherpunks@toad.com
Subject: Re: Are 2048-bit pgp keys really secure ?
In-Reply-To: <199412282004.MAA04125@jobe.shell.portal.com>
Message-ID: <9412290859.ZM12937@wiley.sydney.sgi.com>
MIME-Version: 1.0
Content-Type: text/plain


On Dec 28, 12:04pm, Hal wrote:
> Let us suppose that a 8 MB PC uses parity protection per byte and gets
> one parity error per year of operation.  This is just a guess but I have
> occasionally seen parity errors on PC's and I certainly don't use them
> full time 24 hours a day for a year!

Just a mostly-irrelevant aside...

A somewhat disturbing trend has appeared in the low-end cost-sensitive PC
SIMM market.  Some supposedly 9-bit SIMMs are actually 8-bit SIMMs plus
a parity generator.  This means that the parity checking is essentially
subverted, because the parity bit is generated from the stored contents
of memory at read time, rather than the stored contents when it was
written to.  As such, NO bit errors are detected.

These SIMMs are almost all being produced in Taiwan, and many have the
parity generator marked so that the chip appears to be another DRAM.
It is worth watching out for.

Why are they doing this?  Well, parity generators are much cheaper than
the extra DRAM, and so the manufacturers are saving 15-20% on the production
price.

							Ian.