[Coco] About those EPROMS...

[Mark McDougall]

On 10/04/2015 9:51 AM, Stephen H. Fischer wrote:

> You can use the ROM for random number generation which is all you can use
> it for if you are not the NSA.

Some of the simple 'line scramble' schemes were trivial to reverse-engineer. 
I personally did so on a couple of very early arcade games when I was 
writing the MAME drivers for them - simply by buzzing out the address and 
data lines to/from the ROM on the PCB.

One of them also had a simple XOR 'encryption' which I reverse-engineered 
using brute-force black box analysis.

A bunch of games with much more sophisticated schemes have been 
reverse-engineered by smarter people than me on the MAMEDEV team. Capcom 
CPS2/3 a case in point - even without access to the keys in the CPU the 
encryption was eventually broken after many months of effort. These efforts 
not only allow the games to be emulated, but also allow original arcade 
PCB's that have 'suicided' to be 'phoenixed' (brought back to life), 
allowing the rightful owners to play them again.

So the NSA don't have a monopoly on this sort of activity.

> I think about useful things and have no problem that I was incorrect
> about reading the contents. The silliness of the link also came into
> play.

Not having a go at you at all, simply trying to put the facts out there.

Regards,

-- 
|              Mark McDougall                | "Electrical Engineers do it
|  <http://members.iinet.net.au/~msmcdoug>   |   with less resistance!"