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From: miked@syscon%nstar.rn.com (Mike DeMetz)
Newsgroups: comp.sys.ibm.pc.misc
Subject: Re: printer port key software protection
Message-ID: <1991Feb13.184303.14941@syscon%nstar.rn.com>
Date: 13 Feb 91 18:43:03 GMT
References: <1991Feb13.044757.19348@gpu.utcs.utoronto.ca>
Organization: Syscon International
Lines: 17

tateishi@gpu.utcs.utoronto.ca (Nao Tateishi) writes:



>I need to protect some custom written software but am a little confused.  I've
>looked into the adapters that plug into the printer port and even sent away for
>a demo kit from one company.  After reading the docs, it seems that it shouldn't
>be too hard to create a compatible key.

>Has anyone successfully bypassed these keys or are they as safe as the manuf.
>say they are.
Well their complexity varies.Ones we have(requires 3 to run all levels) use
what looks like a rom.The PC writes a certain code to it and reads back since
the port is bidirectional.Another that I looked at simply feed a pulse back
on pin 10 based on two data ou pulses.The tricky part is there is no 5 volts
on the port so they put out a square wave on a data pin and rectify it for
a power source.