[Cryptography] Data remanence on solid state storage

[Kent Borg]

On 8/18/24 12:06, Ron Garret wrote:
> Worse news: hard (actually impossible) to know for sure what is going on inside*any*  modern electronic device.

Effectively, supply chain attacks.

Very true.

That's why long ago and far away, so to speak, when I once worked for a 
fab-less semiconductor company doing SoCs for laser printers (that dates 
it pretty well), I asked my boss a question that puzzled him. The 
question was roughly: How easily could the fab change our design to add 
a backdoor? He understood the question. What was puzzling was my asking 
it. I don't think anyone else in the company was considering such 
things, and this certainly wasn't my job. But I'm weird, that's why I'm 
on this list.

(Shortish answer, mixing in what I know now: Doable, but involved, and 
even if this were something they were doing to every chip, not cheap. We 
did the design, from IP we bought and our own circuitry, *and* we did 
the layout. I'm pretty sure we only sent the layout to the fab, for we 
wouldn't have had the rights to send higher level "sources" and I don't 
think we were paying them for layout services. So making a change would 
require reverse engineering from our layout, changing the circuit, and 
redoing the layout. Analogous to patching a binary, but harder. We were 
much more at risk of a backdoor in some mostly opaque block that we 
purchased, say our ethernet interface.)


Yes, your point holds, but one can still know a lot about ones gear. 
Magical supply chain criminals aren't going to, say, squeeze 
undocumented TBs of storage or high bandwidth digital transceivers into 
something that doesn't take up enough space, cost enough money, get hot 
enough, draw enough power, nor have the bandwidth to get a hold of ones 
data, etc. Also, at least for users of things like Linux, one can know a 
lot about and influence what data the OS is hurling where. And, in the 
case of SSDs, one can do very powerful things such as never storing 
anything on the SSD that the SSD could differentiate from gibberish. 
I.E., only store encrypted data. (Those links John Gilmore posted did 
not mention using encrypted file systems, alas. Though they were MS 
Windows-centric and I suppose such things are harder over there.)


Supply chain attacks are a very serious problem, but both individually 
and as an industry, we are not completely defenseless.


-kb, the Kent who finally had to bite a bullet he can't really afford 
and order a replacement for his dying laptop, which has him now 
suffering over all the details of how he will set it up, specifically 
around the SSD, and its partitioning and formatting, etc, because that 
is hard to change after-the-fact.

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://www.metzdowd.com/pipermail/cryptography/attachments/20240819/3a51680f/attachment.htm>