Fake Ram: Identifying a Counterfeit Chip

[Robert Baruch‏] had something strange on his hands. He had carefully decapped 74LS189 16×4 static RAM, only to find that it wasn’t a RAM at all. The silicon die inside the plastic package even had analog elements, which is not what one would expect to find in an SRAM. But what was it? A quick tweet brought in the cavalry, in the form of chip analysis expert [Ken Shirriff].

[Ken] immediately realized the part [Robert] had uncovered wasn’t a 74 series chip at all. The power and ground pins were in the wrong places. Even the transistors were small CMOS devices, where a 74 series part would use larger bipolar transistors. The most glaring difference between the mystery device and a real LS819 was the analog elements. The mystery chip had a resistor network, arranged as an R-2R ladder. This configuration is often used as a simple Digital to Analog Converter (DAC).

Further analysis of the part revealed that the DAC was driven by a mask ROM that was itself indexed using a linear feedback shift register. [Ken] used all this information to plot out the analog signal the chip would generate. It turned out to be a rather sorry looking sine wave.

The mystery part didn’t look like any function generator or audio chip of the era. [Ken] had to think about what sort of commodity part would use lookup tables to generate an audio waveform. The answer was as close as his telephone — a DTMF “touch tone” generator, specifically a knockoff of a Mostek MK5085.

Most investigators would have stopped there. Not [Ken] though. He delved into the construction and function of the DTMF generator. You can find the full analysis on his site. This isn’t [Ken’s] first rodeo with decapped chips. He’s previously examined the Intel 8008 and presented a talk on silicon reverse engineering at the 2016 Hackaday Superconference. [Robert] has also shown us how to pop the top of classic ceramic integrated circuits.

 

Counterfeit Hardware May Lead To Malware and Failure

Counterfeit parts are becoming increasingly hard to tell the difference from the real deal, the technology used by the counterfeiters has come on leaps and bounds, so even the experts struggle to tell the real product from a good fake. Mere fake branding isn’t the biggest problem with a counterfeit though, as ieee.com reports, counterfeit parts could contain malware or be downright dangerous.

Way back in 2014 the FBI charged [Marc Heera] with selling clones of the Hondata S300, a plugin engine module for Honda cars that reads sensors, and depending on their values can change idle speed, air-fuel mixture and a plethora of other car/engine related settings. What, might you ask, is the problem, except they are obviously not genuine parts? According to Honda they had a number of issues such as random limits on engine rpm and occasionally failure to start. While the fake Hondata S300 parts where just poor clones that looked the part, anything connected to an engine control unit brings up huge safety concerns and researchers have shown that through ECU access, they could hijack a car’s steering and brakes.

It’s not just car parts being cloned, remember the fake USB-to-serial chips of FTDI-Gate? Entire routers are also being cloned, which doesn’t sound too bad until you realise that the cloners could configure your internet traffic to be redirected through their network for snooping. In 2010 Saudi citizen [Ehab Ashoor] was convicted of buying cloned Cisco Systems gigabit interface converters with the intention of selling them to the U.S Dept of Defense. While nothing sinister was afoot in [Ashoor]’s case other than greed, these routers were to be deployed in Iraq for use by the Marine Corps networks. They were then to be used for security, transmitting troop movements and relaying intelligence from field operations back to HQ.

So who are the cloners and why are they doing it? It is speculated that some of them may be state funded, as there are a lot of countries who do not trust American silicon. Circuits are reverse engineered and find their way to the international market. Then just like the FTDI-Gate case, cloners want to make profits from others intellectual property. This also brings up another question, if there is a mistrust of American silicon, nearly everything is made in China these days so why should we trust anything from there? Even analog circuits can be made to spy on you, as you can see from the piece we recently featured on compromising a processor using an analog charge pump. If you want to defend yourself from such attacks, perhaps look at previous Hackaday Prize finalist, ChipWhisperer.