Maxim Targets IoT with Low Power Coprocessor Toting ChipDNA PUF Technology

September 22, 2021 by Jake Hertz

Security is steadily becoming a top priority, especially at the hardware level. Maxim Integrated hopes to bring both security and low power to IoT applications with its cryptographic processor.

As the world becomes more digital, the risk and fear of cyber security also increase. Security in software design is no longer enough, but rather it is becoming more and more necessary to design hardware with a security focus, down to the silicon level. 

Maxim Integrated, now officially a part of ADI, has been working towards accomplishing precisely that. Earlier this week, the company released a new, low-power cryptographic controller which leverages physically unclonable function (PUF) technology to increase hardware security. This article will take a look at PUF technology and the features of Maxim’s latest cryptographic unit. 


A Refresher on PUFs 

Before diving into Maxim's release, let's talk about PUFs, which is one of the foremost techniques in hardware security. 


PUFs can use a challenge-response pair to authenticate a device.

PUFs can use a challenge-response pair to authenticate a device. Image used courtesy of Sutar et al


PUFs are a hardware security technique that exploits inherent device variations to produce an unclonable, unique device response to a given input. A PUF’s response is unique, random, and repeatable because it can help with cryptographic key generation and “storage,” making it extremely difficult to be compromised on a hardware or software level. 

One major benefit of a PUF is that it is a non-volatile technique, but also it doesn’t physically “store” the key. 

Instead, a PUF creates the key as needed as a challenge-response, which then has the key almost instantaneously erased afterward. As Maxim Integrated put it: “there is always a key, but you can never look at it.” Using PUFs can make for a robust and highly secure cryptographic key storage on the hardware level, which is why Maxim includes it within its security platform: ChipDNA PUF.


Maxim's ChipDNA PUF 

Maxim Integrated is one group that invests significantly into PUF technology, with its flagship offering being its ChipDNA PUF.
ChipDNA works by exploiting the naturally occurring random variation and mismatch of the analog characteristics of CMOS design. The figure below shows a simplified block diagram of the PUF architecture with an example key size of 128 bits.  


Simplified block diagram of ChipDNA PUF architecture.

Simplified block diagram of ChipDNA PUF architecture. Image used courtesy of Maxim Integrated


The diagram above shows a 16 x 16 array of 256 analog PUF elements, which are combined into 128 pairs. Due to process variation, each element will exhibit a random I/V characteristic, which then Maxim uses to generate binary values through a circuit-level comparison of each element of a pair. This process is repeated for all 128 pairs, resulting in a unique, 128-bit key output. 

Most importantly, being a hardware-level security feature, the ChipDNA PUF should be completely immune to all known invasive attacks (i.e., probing) and could thus be a resourceful way of providing hardware-level security.

Now that the general concept of PUFs and Maxim's ChipDNA PUF is understood let's finally delve into the newest release. 


The MAXQ1065 = Low Power and Security 

Maxim's newest security coprocessor, the MAXQ1065, is an ultra-low-power cryptographic controller for IoT. 

Designing for IoT, attaining low power is amongst the most important aspects. The MAXQ1065 achieves this with a power consumption of < 100nA in standby, which Maxim claims allows for 30x lower power compared to similar products. 

The device is intended to provide several security measures, including root-of-trust, mutual authentication, data confidentiality and integrity, and secure boot.


Functional block diagram of the MAXQ1065.

Functional block diagram of the MAXQ1065. Image used courtesy of Maxim Integrated


On top of this, the MAXQ1065 utilizes ChipDNA PUF technology to protect against device-level security attacks. Other hardware security measures include:

  • A true random number generator (TRNG)
  • A TLS/DTLS 1.2 handshake and record layer
  • A 8 kB of secure storage for user data

In the future, Maxim hopes to see the MAXQ1065 utilized in IoT devices in applications like Supervisory Control and Data Acquisition (SCADA), medical equipment, building and home automation, smart city, and smart metering. As the world becomes more connected, it will be pivotal to continue finding this sweet zone between power efficiency and security.