[Coco] About those EPROMS...

[Stephen H. Fischer]

Everything is from my memory decades ago and in this case not very interesting at that time. I was surprised that it was still in use.

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

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.

SHF

----- Original Message ----- 
From: "Mark McDougall" <msmcdoug at iinet.net.au>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Thursday, April 09, 2015 4:34 PM
Subject: Re: [Coco] About those EPROMS...


> On 9/04/2015 11:02 PM, Dave Philipsen wrote:
> 
>> Ok, but the ROM itself, even if encrypted, must be read in order for the
>> program to be executed.  The processor places an address on the address
>> lines, strobes whatever output enables are necessary, and the data at that
>> address appears on the data lines.  Right?
> 
> Of course. Stephen's original statement is a little ambiguous and not 
> technically correct. A ROM has no way of knowing whether you are executing 
> code or reading data. If an external device can read ROM contents - 
> encrypted or not - then so can a 'dumping circuit'.
> 
> Encryption schemes used in the past ranged from simple mangled address 
> and/or data lines to sophisticated block cipher schemes with keys embedded 
> in custom processors, and everything in between. Good examples can be found 
> in retro arcade video games. None of this however changes the fact that the 
> ROM contents can be read directly by simply driving the address bus.
> 
> Regards,
> 
> -- 
> |              Mark McDougall                | "Electrical Engineers do it