From: Bill Stewart <stewarts@ix.netcom.com>
Date: Thu, 11 Apr 1996 02:07:11 +0800
To: Jack Mott <thecrow@iconn.net>
Subject: Re: questions about bits and bytes
Message-ID: <199604100704.AAA21788@toad.com>
MIME-Version: 1.0
Content-Type: text/plain


At 09:33 PM 4/8/96 -0400, Jack Mott wrote:
>This may be a bit of a no brainer, but everything I have read sorta 
>skips over this point.  a bit is 1 or 0.  8 bits make up a byte (0-255).

Be careful writing code - sometimes a byte is -128 to 127 instead of 0 to 255.
Also, there are machines (mostly old kinky ones) that use bytes of sizes
other than
8 bits.

>If I have a 5 byte key, does that make it a 40 bit key? 
 
Not always; bytes may have extra baggage with them such as start&stop bits
(when you're transmitting async), or parity bits.  DES uses 56 bit keys,
but they're really 8 bytes with the high bit of each byte ignored.
But, yeah, 5 bytes is normally 40 bits.

>The only reason this doesn't make sense to me is it seems useless to use 5 byte
>keys, yet that is what companies export since the government limits keys
>to 40 bits.

What's bothering you about it?  The fact that it's not a multiple of 4?
(No problem, think of it as a character string.)  The fact that it's way too
short
to protect any real information, and you've always been taught to use passwords
longer than that, even for computer accounts without real money in them? 
Well, yeah, it is - so what?  A 40-bit key would take few days to crack with
general-purpose 486 or Pentium PCs, though a gate-array would make it easy
to use the right kinds of logic operations to crack it much faster.  

Are you puzzled that the government doesn't care about your ability to
protect your money or your information?  Think if it from their perspective -
if special equipment makes it cost 8 cents to crack a key, they'd probably
have to only crack semi-interesting-looking messages, as opposed to 
hoovering down anything they could find, and wouldn't that be a shame for
National Security....
#					Thanks;  Bill
# Bill Stewart, stewarts@ix.netcom.com, +1-415-442-2215