Fw: Encryption Boards

[Peter Rüb]

Hi,
have also thought about an encryption of custom made eproms.
Could someone explain this to me?
----------
> Von: Land Shark <lndshrk at xmission.com>
> An: diy_efi at coulomb.eng.ohio-state.edu
> Betreff: Re: Encryption Boards
> Datum: Samstag, 25. Oktober 1997 19:35
 
>  Simply the eprom data and address lines are switched 
>  before the image is burned into the EPROM..

OK. No problem. Exchanging blocks in the file and reverse that by a small
board soldered on. Black epoxy keeps from unsoldering.

> 
>  Now the little PAL on the board sees the difference between
>  the SLOW accesses of the burner and the FAST accesses of the
>  CPU and only decrypts if the accesses are FAST

What logic device could do this? Is it a standard type or a special device?
Can i build one myself?

>  
>  Easily broken.. not worth your time!
> 
>  Jim

Thanks,
Peter Rueb
s68558 at stud-mail.uni-wuerzburg.de