From: jim bell <jimbell@pacifier.com>
Date: Sun, 8 Sep 1996 03:10:34 +0800
To: "Chris Adams" <cypherpunks@toad.com>
Subject: Re: What the NSA is patenting
Message-ID: <199609071627.JAA01473@mail.pacifier.com>
MIME-Version: 1.0
Content-Type: text/plain


At 12:18 AM 9/7/96 -0800, Adamsc wrote:
>On Fri, 06 Sep 1996 11:59:18 -0500, John Deters wrote:
>
>>I hope some hardware hacker who knows their low-level stuff will be able to
>>write a secure disk wiper.
>
>They have: it's called a bulk tape eraser. <g>
>
>
>I'd just store everything sensitive on a floppy. Those are easy to erase with a
>heavy duty magnet (not a wimpy refrigerator magnet).  I understand slagging one
>in the microwave is also effective <g>.

Just remember that an AC-driven bulk eraser will be far more effective than 
a permanent magnet at erasing data securely.  An oscillating magnet field 
re-magnetizes the floppy 120 times per second, as opposed to the single 
magnetization done by  the permanent magnet.  Each pass through the 
hysteresis curve brings down residual signals somewhat, maybe 10 db.  With 
the AC field, it's hard NOT to have a good erase.

Jim Bell
jimbell@pacifier.com