Physically Unclonable Function (PUF) research

“[…]Building a hardware product that cannot be copied is hard. Especially small integrated chips make it hard to distinguishing between a knockoff device and a real one. But this is not only a copyright concern, but also important to ensure trust in a device’s origin. For example a chip could be replaced in the manufacturing chain with a backdoored version. A good example to understand the problem is to look at smart cards, especially the ones used for decrypting premium TV channels. The whole business model relies on a shared secret key, embedded inside of the chips. It’s obviously in the interest of the company, that nobody can crate a working copy of such a card. But once the secret key is extracted through various hardware attack techniques, creating a copy of a smart card is trivial. Is there a way how hardware could be manufactured, such that it’s practically impossible to copy – and not just very expensive to copy? Physically Unclonable Function (short: PUF) is a concept that attempts to exploit (utilize) physical impurities, which are different for each device, to make exact physical copies impossible to manufacture. In practice this is often used to verify, that a particular hardware (a chip) is not counterfeit. This is usually implemented with a challenge and response protocol. A vendor can collect valid responses for random challenges of a chip, and the customer can verify later, that the device bought, was really made by that manufacturer. While creating an exact copy of the chip might be impossible, one could try to understand the mathematical model underlaying the behavior and therefor is able to create a device that emulates the behavior of the original chip. Will every PUF have this flaw, that math can describe it’s behavior, or are there PUFs that are truly random and thus unpredictable? – that is an unsolved question. With the experiments I conducted, we tried to understand a certain PUF family better, whose underlaying mathematical model is unknown. […]





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