Re: OTP's

From: Andrew Swallow (am.swallow_at_eatspam.btinternet.com)
Date: 07/25/04 

Date: Sun, 25 Jul 2004 19:19:37 +0000 (UTC)

"Guy Macon" <http://www.guymacon.com> wrote in message
news:10g7a7pn5767hf3@corp.supernews.com...
>
> Rob Warnock <rpw3@rpw3.org> says...
>
> >a covert channel out of the site. [That is, they're worried that some
> >rude program might have hidden a few bits of classified data on them
> >which could be smuggled out of the site, oh my!]
>
> [...]
>
> >Disk drives, of course, are the ultimate "bad" parts -- they're
> >*never* allowed to leave the site intact. But soldered-in UV EPROMS
> >or EEROMs (especially flash EEROMs) are almost as bad.
> >
> >Of course, truly non-alterable ROMs are o.k. (mask-coded bipolar ROMS,
> >for example, or or maybe OTP PROMs with the security fuse blown).
> >
> >This whole thing may seem rather nit-picking to some, but the sites
> >that care about such things are deadly serious about them...
>
> As well they should. People die when security is compromised.
>
> I am curious about the soldered-in UV EPROMS. Do they think that
> the board has the ability to write to them? If they are worried
> about someone unsoldering one, erasing it with UV, putting it in
> a programmer, and hiding secret data in it, they should worry about
> the mask-coded bipolar ROMS as well - someone could hide a microdot
> on the bottom of the chip.

Some UV PROMS can be written to from the CPU. The UV is
only used to blank the chip.

Flash PROMS use used as the memories in flash disks/cards.

Andrew Swallow

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