IOActive had the chance to access the IGS-4215-16T2S device. IOActive identified three vulnerabilities which need attention.
Timeline
2022-09-29: IOActive discovers the vulnerabilities
2023-03-29: IOActive informs Planet Technology about the identified vulnerabilities
2023-12-13: Planet released a new firmware version (1.305b231218) informing IOActive that the vulnerabilities are fixed
2024-01-09: IOActive notifies the vulnerability to INCIBE, Spanish CERT
2024-02-16: IOActive confirm that the vulnerabilities were fixed after retesting them in the new firmware version
2024-03-21: INCIBE shared the CVEs assigned with IOActive
2024-08-07: IOActive advisory published
NOTE : While publishing this disclosure, IOActive had retested version FW-IGS-4215-16T2S_v1.305b231218.bix with hash 6e4ea892dc0d203c83ff02a2cba13e83. This version had the fixes. PLANET Technology published a firmware FW-IGS-4215-16T2S_v1.305b240227.bix with the hash abe64b8a62ebf339fb404fd85c0081b. They had informed that the findings have been fixed in this version. IOActive has not reviewed this firmware.
Fortinet, Inc. (Fortinet) is a global leader of cybersecurity solutions and services that provides protection against cyber threats. It is a company that develops and sells security products and solutions, such as firewalls, endpoint security, intrusion prevention systems, web filtering, antivirus, sandbox, and VPN.
FortiGate is a network security device that provides protection against cyber threats. The device can perform various functions, such as, firewall, intrusion prevention system, web content filtering, antivirus, sandbox and VPN and is part of the Fortinet Security Fabric, which integrates different security products and services into a unified and automated platform.
Timeline
2023-11-16: IOActive discovers the vulnerability
2023-11-22: IOActive informs Fortinet about the identified vulnerability
Bits to Binary to Bootloader to Glitch: Exploiting ROM for Non-invasive Attacks
By
Tony Moor
In this paper, we explore how ROM can be leveraged to perform a non-invasive attack (i.e., voltage glitching) by a relatively unsophisticated actor without a six-figure budget. We begin by explaining what ROM is, why it is used, and how it can be extracted.
What exactly is ROM?
Put simply, Read-Only Memory (ROM) is a type of Non-Volatile Memory (NVM) that is constructed as physical structures within chips. The structures are patterned as ones and zeroes on one, and only one, of several layers of the chip. Why just one? Cost. ROM is real hardware, and making any hardware changes in the layout of a chip is very expensive.
The fact that ROM is physically encoded in a chip makes it uniquely reliable and thus appropriate for critical functions, such as boot code execution. ROM is infinitely more reliable than NVM that relies on an electrical charge, like Flash.
The following table provides a brief overview of memory classes.
How can you extract data from ROM?
If there is no protection on the device (i.e., it is embedded on a development board), then it is simple to access the data and dump it as a binary (.bin) file. By doing so, we have essentially extracted the final code, as opposed to the raw bits. This means that the code is in an understandable format (no need to decrypt or descramble) and can be analyzed using standard software reverse engineering tools, like IDA Pro or Binary Ninja, to isolate a weakness in the bootloader.
If the ROM is protected, then there is the option to physically deprocess sample chips (more on that later) and extract the raw bits as ones and zeroes. The process is very skill dependent; however, it is possible to carry out on a shoestring budget depending on the age of the chip technology. In some cases, only a polishing wheel, a handheld polishing jig, and an optical microscope are needed.
Reading out the raw bits is only the first step of the process, as these bits need to be further analyzed and manipulated to properly understand the code. The complexity of reverse engineering will vary depending on the following:
Is the ROM scrambled?
Scrambling is when the data is ‘mixed-up’ at the periphery of the memory block. In this case, it is enough to study the peripheral circuitry to make sense of the data.
The ordering may also vary byte-to-byte, making reverse engineering more difficult.
Is the ROM encrypted?
Encryption is far more difficult to reverse engineer because the data is routed out of the memory and into the CPU logic, which is usually vast and, on its face, random. The data will be routed to the decryption circuitry, which may only be a few dozen logic cells.
Finding the decryption circuitry in a sea of one hundred thousand logic cells with no direction on where to start is an extremely difficult task. It may be necessary to reverse engineer the entire CPU logic; however, there are isolation techniques like thermal or photon emission that can help identify a specific area of interest on the chip. Using such techniques, the chip is instructed to repeatedly decrypt data while the entire chip is monitored for heat or light emissions, revealing the area of the chip that is performing the decryption. This smaller area of the chip then becomes the focus of reverse engineering.
Is the ROM both scrambled and encrypted?
If the ROM is both scrambled and encrypted, recovering the data will require analysis of the addressing logic and reverse engineering some if not all of the CPU logic. If the raw data is encrypted, the physical bit pattern will look the same, whether it is scrambled or not.
How do you deprocess a chip?
Deprocessing is the physical removal of layers from a finished chip using chemical and mechanical techniques. The process is necessarily destructive and can be used to remove one or more layers, depending on the target.
Consider the following example chip:
We can see that the chip is constructed of many layers of copper circuitry, all embedded in an insulator (glass-type material). Transistors are literally the building blocks of digital components and are fabricated on the silicon substrate at the bottom of the chip. Therefore, the ROM transistors will be located on the bottom as well. The raw bits we are looking for (the ROM encoding layer) will likely be at the Contact, Metal 1, or Via 1 layer (between Metal 1 and Metal 2), but we won’t know for sure until we start destroying some chips.
If we have the time and sufficient samples, we can start by removing all of the layers from one chip in order to analyze the floorplan. Based on this analysis, we can map out where the memories are located and even identify what types of memories are present, such as Flash, SRAM, DRAM, or ROM. This will help identify the specific area of the chip to focus on when attempting to extract the raw bits. In addition, we could also cross-section a chip at the location of the ROM to help determine which layer contains the bit encoding to guide our work.
If we don’t have the time or the samples, we can just go ahead and carefully deprocess a single chip, and at some point, the ROM bits will appear. But if we deprocess too far, we will go past the bit encoding layer and lose the data.
For our work, we will use the most basic and fastest technique—mechanical polishing. While many argue that mechanical polishing is the most effective method for deprocessing chips, it is also the most skill dependent.
We can polish in several ways (in order of increasing sophistication and cost):
Manual finger polishing: The decapsulated chip is placed on the fingertip and polished on a static plate or piece of glass.
Turntable finger polishing: Similar to manual but uses a rotating platen to expedite the polishing process (and eliminate Repetitive Strain Injury!).
Manual polishing with fixture (jig): Uses a rotating platen in conjunction with a polishing fixture that can be adjusted to compensate for non-planarity.
In this example we used the third approach because a turntable accelerates progress, and a polishing jig offers fine angle control. Additionally, the manual polishing table and jig, as well as the abrasives involved, are relatively low-cost items, keeping the approach within reach of a skilled and motivated hobbyist.
Determining when to stop polishing (end pointing) is difficult; however, when we hit the ROM encoding layer, we should see some kind of pattern under an optical microscope, even at 5x magnification.
The image below was taken at 20x magnification, and we can categorically say that we have reached the right layer.
The bits appear as white dots from above, because they are bullet-shaped Tungsten interconnects, a little like the contacts shown in the following cross-section images:
We can see from a very high-level visual inspection that the ROM cannot possibly be encrypted, due to the distribution of ones versus zeroes. If the data was properly encrypted, then the distribution would appear random; however, a visual assessment is sufficient to confirm a lack of entropy without the need to formally calculate[1] it with binwalk[2] or another tool. We can conclude that although the data may be scrambled, it is not encrypted. There is enough evidence to tell us that if we extract the raw bits, we can derive the addressing to then get us back to an understandable binary.
For now, we don’t need to carefully analyze the addressing circuit; all we need is to determine if there is any scrambling in the addressing logic. We can do this visually.
When we isolate a small area of the decoding/addressing circuitry at any point (bottom, left, or between the blocks), it is perfectly repeated. This proves that the ROM is not scrambled, and all we need to do is to work out how the bits are read to recreate the full binary. That, and extract the raw bits, of course.
No Scrambling 😊
No Encryption 😊
How do you extract the raw bits?
It is preferable that we automate the extraction process, as the ROM’s capacity is 16 KB (128,000 single bits), which is far too much to extract manually. First, we must determine if our optical images are good enough to reliably extract the raw bits. If not, we may need to use a Scanning Electron Microscope (SEM) to obtain higher resolution, higher contrast images.
Clearly there is a huge difference in resolution and, more importantly, contrast between the two types of images. It’s obvious that using SEM images would expedite the extraction process, but let’s see if we can use the optical images and do this on a shoestring budget.
First, we need to optimize the optical test image with photo editing software to maximize our chances of success. A good start is always to use the filters in Photoshop such as ‘Noise – Despeckle’ and ‘Noise – Dust and Scratches.’ The final step would be to manipulate the levels to maximize the contrast.
Perhaps quite surprisingly, simply by filtering and adjusting the levels of the optical image, we can almost end up with the same result as with the SEM.
From this simple test, we can conclude that any effective tool will be capable of reliably extracting the raw bits from our optical images.
Commercial software is available for semi-automated ROM bit extraction. The software measures the brightness of the area around the line intersections and compares that against a user-defined estimate for both a one and a zero. The software then assigns values to each area in which a bit exists, then exports the values to a text file. Below is the text extracted from this small piece of ROM. This is a fraction of one of 64 sections within the memory array, so some time is required for a full extraction. There is certainly an AI/ML opportunity here to expedite the process.
After repeating the process many times, we have the entire ROM in our hands, and we can move onto the next step: deriving how the bits are addressed. At this point, we will have a usable binary to work with in IDA Pro or Binary Ninja so we can understand the boot process and find some potential areas of weakness we can glitch.
Bits to Binary
As this is a chip with a known vulnerability, it was possible to dump the entire ROM via JTAG. We will use this dump to help us do two things:
Deduce how the ROM is addressed
Compare our physically extracted ROM with the JTAG dump to validate our process
To illustrate the analysis of our physically extracted dump, we will use the higher-resolution SEM images we acquired after the optical images were taken.
Let’s start by looking at the electrical dump of the ROM. The following output is the beginning and end of the ROM .bin, with the end looking very much like a checksum. We know this is commonly used by this manufacturer, so after many zero bytes, there are two bytes of data at the very end of the file.
From the fact that we have the two-byte checksum (0105) in hex, and that the corresponding raw bits (0000 0001 0000 0101) are not in a linear pattern, then we must assume that there is some flipping/mirroring happening on the bit addressing. The fact that the bits are split over two rows also gives us a clue.
Now our checksum is beginning to make sense. With a checksum of 0105 (0000 0001 0000 0101), there must only be one way to read it. Essentially, we are looking for how the three ones are addressed.
First, we can see that the three bits are all on the same bit column, so we can ignore the rest. It makes things easier to visualize by annotating all of the bit columns, then highlighting the only column (column 0) we care about in yellow. The values are now much easier to read by eye, and we can see the direction in which they are read by the memory array.
We now see that 0105, albeit not in a logical order for a human. There is one question mark remaining: Do we assume that we read the left side in reverse first (01) followed by the second (05)? There we have a simple 50% chance of being correct, and to find out, we can apply that to the more densely populated areas of ROM.
The portion of ROM above shows the hex value along with the raw binary for the two-word width of the ROM array. The colored arrows illustrate the direction in which the bits are read from the .bin and how they are read from the raw bit image. The following is a closer view of one byte, where blue bits are logical ones and yellows are logical zeros:
Finally, a binary!!!
The following image contains some dumped bytes from the target. This can be later be opened in the reversing tool of our choice, and after some preparation work, we can begin reverse engineering and identifying the potential weaknesses. In this case, as some readers might know, the target sample has a known vulnerability that can be exploited via fault injection. This vulnerability can allow an attacker with physical access to the device to retrieve the entire contents, even if the chip has been locked down.
Overall Conclusions
While a chip with a known vulnerability was used in this case study for comparative purposes, the same techniques can be applied to a chip without this vulnerability
The electrical version of the ROM dump matched 100% with the physically extracted version
Physical ROM bit extraction is skill-dependent, but can be carried out using a relatively basic toolset such as:
Basic polishing turntable
Handheld polishing jig
Diamond abrasives
Optical microscope
ROM binary extraction is dependent on:
Existence of encryption
Complexity of scrambling
Patience!
ROM binary analysis and isolation of glitching/fault injection points is possible
Electrical and electromagnetic fault injection techniques are skill- and chip-dependent; however, the bar of entry is relatively low (hundreds to thousands of dollars)
In this post, we continue our deep dive comparison of the security processors used on a consumer product and an unlicensed clone. Our focus here will be identifying and characterizing memory arrays.
Given a suitably deprocessed sample, memories can often be recognized as such under low magnification because of their smooth, regular appearance with distinct row/address decode logic on the perimeter, as compared to analog circuitry (which contains many large elements, such as capacitors and inductors) or autorouted digital logic (fine-grained, irregular structure).
Identifying memories and classifying them as to type, allows the analyst to determine which ones may contain data relevant to system security and assess the difficulty and complexity of extracting their content.
OEM Component
Initial low-magnification imaging of the OEM secure element identified 13 structures with a uniform, regular appearance consistent with memory.
Higher magnification imaging resulted in three of these structures being reclassified as non-memory (two as logic and one as analog), leaving 10 actual memories.
Of the remaining 10 memories, five distinct bit cell structures were identified:
Single-port (6T) SRAM
Dual-port (8T) SRAM
Mask ROM
3T antifuse
Floating gate NOR flash
Single-port SRAM
13 instances of this IP were found in various sized arrays, with capacities ranging from 20 bits x 8 rows to 130 bits x 128 rows.
Some of these memories include extra columns, which appear to be intended as spares for remapping bad columns. This is a common practice in the semiconductor industry to improve yield: memories typically cover a significant fraction of the die surface and thus are responsible for a large fraction of manufacturing defects. If the device can remain operable despite a defect in a memory array, the overall yield of usable chips will be higher.
Dual-port SRAM
Six instances of this IP were found, each containing 320 bit cells (40 bytes).
Mask ROM
Two instances of this IP were found, with capacities of 256 Kbits and 320 Kbits respectively. No data was visible in a substrate view of the array.
A cross section (Figure 7) showed irregular metal 1 patterns as well as contacts that did not go to any wires on metal 1, strongly suggesting this was a metal 1 programmed ROM. A plan view of metal 1 (Figure 8) confirms this. The metal 1 pattern also shows that the transistors are connected in series strings of 8 bits (with each transistor in the string either shorted by metal or not, in order to encode a logic 0 or 1 value), completing the classification of this memory as a metal 1 programmed NAND ROM.
IOActive successfully extracted the contents of both ROMs and determined that they were encrypted. Further reverse engineering would be necessary to locate the decryption circuitry in order to make use of the dumps.
Antifuse
Five instances of this IP were found, four with a capacity of 4 rows x 32 bits (128 bits) and one with a capacity of 32 rows x 64 bits (2048 bits).
The bit cells consist of three transistors (two in series and one separate) and likely function by gate dielectric breakdown: during programming, high voltage applied between a MOSFET gate and the channel causes the dielectric to rupture, creating a short circuit between the drain and gate terminals.
Antifuse memory is one-time programmable and is expensive due to the very low density (significantly larger bit cell compared to flash or ROM); however, it offers some additional security because the ruptured dielectric is too thin to see in a top-down view of the array, rendering it difficult to extract the contents of the bit cells. It is also commonly used for small memories when the complexity and re-programmability of flash memory is unnecessary, such as for storing trim values for analog blocks or remapping data for repairing manufacturing defects in SRAM arrays.
Flash
A single instance of this IP was found, with a capacity of 1520 Kbits.
This memory uses floating-gate bit cells connected in a NOR topology, as is common for embedded flash memories on microcontrollers.
Clone Component
Floorplan Overview
The secure element from the clone device contains three obvious memories, located at the top right, bottom left, and bottom right corners.
Lower-left Memory
The lower-left memory consists of a bit cell array with addressing logic at the top, left, and right sides. Looking closely, it appears to be part of a larger rectangular block that contains a large region of analog circuitry above the memory, as well as a small amount of digital logic.
This is consistent with the memory being some sort of flash (likely the primary code and data storage for the processor). The large analog block is probably the high voltage generation for the program/erase circuitry, while the small digital block likely controls timing of program/erase operations.
The array appears to be structured as 32 bits (plus 2 dummy or ECC columns) x 64 blocks wide, by 2 bits * 202 rows (likely 192 + 2 dummy features + 8 spare). This gives an estimated usable array capacity of 786432 bits (98304 bytes, 96kB).
A cross section was taken, which did not show floating gates (as compared to the OEM component). This suggests that this component is likely using a SONOS bit cell or similar charge-trapping technology.
Lower-right Memory
The lower-right memory consists of two identical blocks side-by-side, mirrored left-to-right. Each block consists of 128 columns x 64 cells x 3 blocks high, for a total capacity of 49152 bits (6144 bits, 6 kB).
At higher magnification, we can see that the individual bit cells consist of eight transistors, indicative of dual-port SRAM—perhaps some sort of cache or register file.
Upper-right Memory
The upper – right memory consists of a 2 x 2 grid of identical tiles, each 128 columns x 160 rows (total capacity 81920 bits/10240 bytes/10 kB).
Upon closer inspection, the bit cell consists of six transistors arranged in a classic single-port SRAM structure.
Concluding Remarks
The OEM component contains two more memory types (mask ROM and antifuse) than the clone component. It has double the flash memory and nearly triple the persistent storage (combined mask ROM and flash) capacity of the clone, but slightly less SRAM.
Overall, the memory technology of the clone component is significantly simpler and lower cost.
Overall Conclusions
OEMs secure their accessory markets for the following reasons:
To ensure an optimal user experience for their customers
To maintain the integrity of their platform
To secure their customers’ personal data
To secure revenue from accessory sales
OEMs routinely use security chips to protect their platforms and accessories; cost is an issue for OEMs when securing their platforms, which potentially can lead to their security being compromised.
Third-party solution providers, on the other hand:
Invest in their own labs and expertise to extract the IP necessary to make compatible solutions
Employ varied attack vectors with barriers of entry ranging from non-invasive toolsets at a cost of $1,000 up, to an invasive, transistor-level Silicon Lab at a cost of several million dollars
Often also incorporate a security chip to secure their own solutions, and to in turn lock out their competitors
Aim to hack the platform and have the third-party accessory market to themselves for as long as possible
Research-fueled Security Assessments and Advisory Services
IOActive has been at the forefront of cybersecurity and testing services since 1998. Backed by our award-winning research, our services have been trusted globally by enterprises and product manufacturers across a wide variety of industries and in the most complex of environments.
Tailored to meet each unique organization’s requirements, IOActive services offer deep expertise and insight from an attacker’s perspective.
Security services for your business, situation, and risks.
With our breadth and depth of services offerings across more environments than any other firm today, we can deliver specific, high-value recommendations based on your business, unique situation, and the risk you face. We are a pure-play security services provider, offering services across the spectrum to include: cybersecurity advisory, full-stack security assessments, SDL, red/purple team and security team development (training) services.
What I’m writing here isn’t about whether you should be in the cloud or not. That’s a complex question, it’s highly dependent on your business, and experts could still disagree even after seeing all of the inputs
What I want to talk about is two distinct considerations when looking at the risk of moving your entire company to the cloud. There are many companies doing this, especially in the Bay Area. CRM, HR, Email—it’s all cloud, and the number of cloud vendors totals in the hundreds, perhaps even thousands.
We’re pretty familiar with one type of risk, which is that between the internet and the cloud vendor. That list of risks looks something like this:
The vendor is compromised due to a vulnerability
An insider at the vendor leaves with a bunch of data and sells or posts it
Someone at the vendor misconfigures something and the internet finds it
The list goes on from there.
But the side of that cloud/vendor risk that companies don’t seem to be as aware of is their own insider access: while one risk is that the vendor does something stupid with your data, another is that your own employees do the same.
Considerations around insider access are numerous:
Employees with way too much access to sales, customer, employee, financial, and other types of data
No ability to know whether that data is being downloaded, by whom, and how much
No ability to detect that data on endpoints
No control of which endpoints access the data
No ability to control where that data is then sent
The situation in so many cloud-based companies is that they enable business by providing access to these cloud systems, but they don’t control which endpoints can reach that data. Users may get in through web apps, mobile apps, or other means. It’s application-based authentication that doesn’t know (or care) what type of device is being used: a 12-year-old desktop with XP on it, or an old Android device that hasn’t been updated in months or years.
Even worse is the false sense of security gained from spending millions on firewall infrastructure, while a massive percentage of the workforce either doesn’t work at the office or doesn’t hairpin back into the office through a VPN. The modern workforce—especially in these types of environments—increasingly connects from a laptop at home (or at a co-work site or coffee shop) directly to the backend, which is the cloud.
This puts us increasingly in a situation where most of the NetSec products we’ve been investing in for the last 15 years are moot, for the simple reason that fewer and fewer people are using the corporate network.
For cloud-based companies especially, it’s time to start thinking about AuthZ and AuthN from not just the user and app perspective, but from a complete endpoint perspective. What is the device, OS, patch levels, malware controls, etc., combined with the user auth, for any given access to an application and the data within?
The risk from a compromised vendor is significant, but it’s also largely outside of a company’s control. Anyone who’s been in security for a while knows that there are thousands of companies with X, Y, or Z certifications, or positive audit results when they absolutely shouldn’t have passed. It’s really hard to know how safe your data is when it’s sitting with hundreds of cloud vendors.
What you can do is to get better control over what your own people are doing with that same data, and that starts with understanding who’s accessing it, and from what devices.
IOActive Announces Acquisition of Flylogic Engineering and Hardware Security Lab
World-renowned Semiconductor Security Expert, Christopher, Tarnovsky, to Head IOActive’s Expanded Hardware Division
Seattle, WA—July 26, 2012. IOActive, a a global leader in information security services and research, today announced the acquisition of Flylogic Engineering and its assets, in addition to the appointment of Christopher Tarnovsky as IOActive’s Vice President of Semiconductor Security Services. In conjunction with this announcement, IOActive will be opening an expanded hardware and semiconductor security lab in San Diego, California.
Flylogic and Mr. Tarnovsky have long been at the forefront of this industry, building a world-renowned reputation for delivering high-quality semiconductor assessments to some of the most respected organizations in the world. With this acquisition, IOActive will be opening a new multi-million dollar hardware campus in San Diego. This lab will serve as both a training facility and home for Flylogic’s expansive hardware needs, including tools such as a Focused Ion-Beam Workstation (FIB) and Scanning Electron Microscope (SEM).
Advances in embedded device manufacturing have resulted in smaller, faster, and more enhanced chips. As a result, supply chain security has become even more critical to forward-thinking enterprises: It is clear that investing solely in software security is no longer enough to combat today’s sophisticated attackers. The new-generation attacker has targeted the silicon, embedding hidden gates and/or backdoors at the electron level that could allow any system appointed with the technology to be quietly compromised far outside the realm of the asset holder to ever detect.
With this acquisition, IOActive is the only leading international boutique security firm in the world with the capability to review chips at the silicon level in-house, using world-acknowledged and -accredited experts while leveraging our best-of-breed software security experts. The expansion of the San Diego lab will allow Tarnovsky and his team to focus on performing these types of extensive semiconductor risk assessments and provide the necessary insights to drive the shift toward more secure chipsets.
“The passion and skill Chris has for his work mirrors what IOActive’s team has long been known for. He has a keen eye and unmatched skill for breaking semiconductors, coupled with a strong desire to help his clients be more secure,” said Jennifer Steffens, Chief Executive Officer of IOActive. “What he has accomplished with Flylogic is amazing; we are thrilled to be forming this unified team and to provide the support needed to bring services to the next level.”
“I’ve had the pleasure of getting to know IOActive over the last few years and the timing couldn’t be better for this announcement. They continue to break the barriers of what is expected from security firms and with their backbone of support, our semiconductor security assessments can continue to surpass all expectations,” said Chris Tarnovsky, owner of Flylogic and now VP of Semiconductor Security at IOActive. “I’m excited to work with them as we strive to improve the security landscape overall.”
Christopher Tarnovsky will be available to discuss Flylogic and the acquisition in IOActive’s IOAsis suite at Caesars Palace.
About IOActive
Established in 1998, IOActive is an industry leader that offers comprehensive computer security services with specializations in smart grid technologies, software assurance, and compliance. Boasting a well-rounded and diverse clientele, IOActive works with a majority of Global 500 companies including power and utility, hardware, retail, financial, media, aerospace, high-tech, and software development organizations. As a home for highly skilled and experienced professionals, IOActive attracts talented consultants who contribute to the growing body of security knowledge by speaking at such elite conferences as Black Hat, Ruxcon, Defcon, BlueHat, CanSec, and WhatTheHack. For more information, visit www.ioactive.com.
4 Metal, 350 nanometer fabrication process, EAL4+ smart card. A device fabricated in 2002 and yet, today the latest ST19W/N series only main differences are the ROM data bus output width into the decrypt block and the fabrication process (180nm and 150nm shrink).
The device was dipped into a HydroFluoric (HF) bath until the active shielding fell off. The result of this saved about 10 minutes of polishing to remove the surface oxide and Metal 4 (M4). This also helps begin the polishing process on the lower layers fairly evenly.
The oxide thickness of a layer once the passivation oxide is removed requires less than 2 minutes per layer to remove. We purposely stop just before the Metal 3 (M3) surface is exposed leaving the vias visibly clear (there are several gates tied to the ground of the mesh on Metal 4 (M4) as well as the active shield’s begin and end vias.
The device was very modularly placed n’ routed. The MAP consists of asymmetric and symmetric crypto functions (DES, RSA, etc).
The EEPROM control logic is actually in the lower left corner of the EEPROM block.
As Metal 3 (M3) was removed exposing the M2 layer, the device is beginning to not look so complicated.
Metal 1 (M1) shows us all the transistors. We did not polish down to the poly. Most of the gates are understandable without it for the purposes of finding the clear data bus.
Most likely, these NVM areas in Figure 7 & 8 are trimming or security violation related. No further investigation is planned on these areas (it isn’t necessary).
Strangely enough, it is now understandable why ST cannot achieve high performance on the ST19 platform. Each logic area with access to the clear data bus runs via a high-output driver that is tri-stated (hi-z) when not driven. This means that all drivers are OR-tied and only one set of 8 drivers are ever active at a time. This is a very large and cumbersome way of creating a MUX.
As time permits, the ST19W and ST19N series will be looked at. It is expected to again find this kind of pattern. Overall, finding the clear data bus took 1.5 hours once the images were created. Most of the 1.5 hours was the alignment of the layers.
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