Using IC can a CPU (Core) be obfuscated on die ?

Thread Starter

VictorX6799

Joined Oct 21, 2015
3
Just a hypothetical question I've always wanted to know if it is possible for a CPU (Core) to be hidden by the manufacturer ? I'm thinking mainly in terms of desktop CPU manufacturers such as Intel and AMD.
 

BobTPH

Joined Jun 5, 2013
4,738
It is certainly possible that a chip might have more cores than claimed and that one or more is disabled. It s not likely that it is being used for some nefarious purpose, if that is where you are heading.

Bob
 

Victor6799

Joined Aug 30, 2011
1
It is certainly possible that a chip might have more cores than claimed and that one or more is disabled. It s not likely that it is being used for some nefarious purpose, if that is where you are heading.

Bob
No actually I was just thinking that a hidden core on die might be designed in such a way so that anyone trying to reverse engineer the CHIP may have a difficult time in locating it when attempting to reverse the entire chip in order to steal IP (Intellectual Property) details.
 

dl324

Joined Mar 30, 2015
14,302
No actually I was just thinking that a hidden core on die might be designed in such a way so that anyone trying to reverse engineer the CHIP may have a difficult time in locating it when attempting to reverse the entire chip in order to steal IP (Intellectual Property) details.
There is no way to prevent that, but anyone doing that would be missing the recipe for the process (implant concentrations, temperatures, angles, optical proximity correction, "light" source used for each layer, gate first/last, etc). Plus, you have billions of transistors to deal with and more than a dozen layers.

Regarding whether there might be cores on the die that aren't being used - that is very possible. When Intel made a 4 core part, they could disable functional cores for part numbers that had fewer cores (e.g. i3). They could also have down binned parts to sell faster parts at slower speeds. They once had a strategy of selling "upgrades" that would unlock features like higher clock speeds, hyperthreading, more cores, etc.
 

drjohsmith

Joined Dec 13, 2021
376
Yes is easy answer,
i.e. the first useful processor, the 4004, has around 2K transistors,
that could well be lost in the 3 Billion plus in say a i7

But if an anti copy protection was needed,
then who needs a processor ?
 

bloguetronica

Joined Apr 27, 2007
1,521
If I recall correctly, cores are routinely disabled and hidden during binning, because they failed some tests. For instance, Intel can sell 6 core i7s as 4 core CPUs, if two cores fail.
 

dl324

Joined Mar 30, 2015
14,302
But if an anti copy protection was needed,
then who needs a processor ?
They do need protection from copying. In the 80's a copyright symbol for masks was created. It doesn't stop anyone from trying to reverse engineer a part, but it makes it illegal in all countries that honor IP marked with the mask copyright. Even where copying is allowed, the companies can lobby the US Government to take appropriate actions against the country where the theft occurred.
 

nsaspook

Joined Aug 27, 2009
9,435
Some of the not so hidden mask pre-copyright era marks were cool ...
1640708148327.png

https://en.wikipedia.org/wiki/Semiconductor_Chip_Protection_Act_of_1984
Prior to 1984, it was not necessarily illegal to produce a competing chip with an identical layout. As the legislative history for the SCPA explained, patent and copyright protection for chip layouts, chip topographies, was largely unavailable.[1] This led to considerable complaint by U.S. chip manufacturers—notably, Intel, which, along with the Semiconductor Industry Association (SIA), took the lead in seeking remedial legislation—against what they termed "chip piracy." During the hearings that led to enactment of the SCPA, chip industry representatives asserted that a pirate could copy a chip design for $100,000 in 3 to 5 months that had cost its original manufacturer upwards of $1 million to design.[2]
 

drjohsmith

Joined Dec 13, 2021
376
They do need protection from copying. In the 80's a copyright symbol for masks was created. It doesn't stop anyone from trying to reverse engineer a part, but it makes it illegal in all countries that honor IP marked with the mask copyright. Even where copying is allowed, the companies can lobby the US Government to take appropriate actions against the country where the theft occurred.
Agreed, but the OP asked about a CPU "obfuscated" on a die,
for which we are guessing why they are asking,
one idea was that it is for IP protection,
 

dl324

Joined Mar 30, 2015
14,302
Some of the not so hidden mask pre-copyright era marks were cool ...
That was pretty common in the 80's and before. The company I worked for put a ban on that, but mask designers would still manage to put their marks in the layout. I knew one buy who made his initials in some metal tracks that were part of the circuit. Anyone looking at them might think it was just coincidence, but it wasn't.
 

dl324

Joined Mar 30, 2015
14,302
Agreed, but the OP asked about a CPU "obfuscated" on a die,
for which we are guessing why they are asking,
one idea was that it is for IP protection,
It wasn't uncommon for some unnecessary circuitry to be added to the layout. If someone copied it without analyzing the circuitry, they wouldn't know it didn't serve any purpose other than to help catch copiers.
 

k1ng 1337

Joined Sep 11, 2020
413
No actually I was just thinking that a hidden core on die might be designed in such a way so that anyone trying to reverse engineer the CHIP may have a difficult time in locating it when attempting to reverse the entire chip in order to steal IP (Intellectual Prop
It wasn't uncommon for some unnecessary circuitry to be added to the layout. If someone copied it without analyzing the circuitry, they wouldn't know it didn't serve any purpose other than to help catch copiers.
Having just a few disguised / false traces in addition to some useless components would be a good way to foil the would be thief's circuit in a puff of smoke.
 

ronsimpson

Joined Oct 7, 2019
1,996
I can not see how hiding a "core" will make reverse engineering harder. It is like writing "do not copy" on a document.

I used a IC that had a 8051 core for interface and a DSP core deep inside that the users were not to know about.
 
Top