---- START NEW MESSAGE ---
Received: from cherry.ease.lsoft.com [209.119.0.109] by dpmail10.doteasy.com with ESMTP
  (SMTPD32-8.05) id AB2735D300D2; Thu, 29 Jan 2004 04:23:03 -0800
Received: from PEAR.EASE.LSOFT.COM (209.119.0.19) by cherry.ease.lsoft.com (LSMTP for Digital Unix v1.1b) with SMTP id <7.00CC299D@cherry.ease.lsoft.com>; Thu, 29 Jan 2004 7:22:54 -0500
Received: from MITVMA.MIT.EDU by MITVMA.MIT.EDU (LISTSERV-TCP/IP release 1.8e)
          with spool id 2420 for PICLIST@MITVMA.MIT.EDU; Thu, 29 Jan 2004
          07:22:49 -0500
Received: from MITVMA (NJE origin SMTP@MITVMA) by MITVMA.MIT.EDU (LMail
          V1.2d/1.8d) with BSMTP id 8185; Thu, 29 Jan 2004 07:22:09 -0500
Received: from dwalin.rl.ac.uk [130.246.135.131] by mitvma.mit.edu (IBM VM SMTP
          Level 430) via TCP with ESMTP ; Thu, 29 Jan 2004 07:22:08 EST
X-Comment: mitvma.mit.edu: Mail was sent by dwalin.rl.ac.uk
X-RAL-MFrom: <A.B.Pearce@rl.ac.uk>
X-RAL-Connect: <sstdwkiwi.ag.rl.ac.uk [130.246.189.231]>
Received: from sstdwkiwi (sstdwkiwi.ag.rl.ac.uk [130.246.189.231]) by
          dwalin.rl.ac.uk (8.12.8/8.12.8) with SMTP id i0TCJpsj028258 for
          <PICLIST@MITVMA.MIT.EDU>; Thu, 29 Jan 2004 12:19:51 GMT
References: <2193429B07D9914D97216EBBAA6AB8BD1A04DB@whitlam.corp.gli.com.au> 
            <017d01c3e604$0ed1e440$7b01a8c0@Paradise>
MIME-Version: 1.0
Content-Type: text/plain; charset="Windows-1252"
Content-Transfer-Encoding: 7bit
X-Priority: 3
X-MSMail-Priority: Normal
X-Mailer: Microsoft Outlook Express 6.00.2800.1106
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106
X-CCLRC-SPAM-report: -4.9 : BAYES_00
X-Scanned-By: MIMEDefang 2.35
Message-ID:  <151001c3e662$31b1df70$e7bdf682@space.rl.ac.uk>
Date:         Thu, 29 Jan 2004 12:19:51 -0000
Reply-To:     pic microcontroller discussion list <PICLIST@MITVMA.MIT.EDU>
Sender:       pic microcontroller discussion list <PICLIST@MITVMA.MIT.EDU>
From:         "Alan B. Pearce" <A.B.Pearce@RL.AC.UK>
Subject: Re: [PIC:] Disassemblers
To:           PICLIST@MITVMA.MIT.EDU
Precedence: list
X-RCPT-TO: <mailinglist2@FARCITE.NET>
Status: U
X-UIDL: 371856245

>- Amount of money requested "unusual" or reacts with PIN in some way.
>    This would be one of the easiest but hard to spot and unlikely to be
>fluked by others.
>
>    eg PIN = 3141 & amount = $79.69   = trapdoor on (can you see how)
>         Only one chance in 10,000 of this being a fluke.
>        Could be MUCH more subtle.
>
>        eg PIN = 3141 & amount = $5.06 (almost uncrackable)
>        (ie $ = Subtract PIN digits from 10, dec/inc/dec/inc digits, shift
>right once.)

This would be easily entered, and identifiable as a trapdoor, as the decimal
key is not used when entering the amount of money, as it needs to be an
integer.

Another trapdoor would be, say the smallest note is a $10, then entering
anything other than a zero as the last digit starts the trapdoor code, and
the last digit gets sent off as a 0 to the host machine.

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.

.