# Tag Info

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A company can make more money if the printers it sells only work with the cartridges they sell, which does not work if there is competition. It's cheaper to force a vendor lock-in than it is to innovate and ensure that your product holds up to the competition. All the printer's authentication does is prevent you from using cartridges made by other companies. ...

4

At least in the Intel ISSCC 2014 paper, including with access to the 7 figures, I do not see that the PUF block has any kind of variable input. The aim of the PUF and accompanying circuitry seems to be: generate a small random value that is mostly rooted in imbalances of the silicon manufacturing process, rather than injected by a test procedure; remains ...

4

The answer lies in "complexity", but I do not believe they are unclonable in the explicit sense, but I can think of ways to get data out depending on how they are made. It is easy for me to see "ROM" type gates under a SEM, and what PUFs buy you is that the structure is uniform but then you do not know the electrical characteristics. In a PUF array, you ...

3

In the article, "weak PUFs" are for key storage, and "strong PUFs" are for authentication, but both are PUFs. It's just a function of how you use them. A 32-bit PUF is just a random 32-bit number. What makes a weak PUF strong is pairing it with an HMAC circuit, or something for a challenge response. A few notes on the article: the ...

2

The chip user doesn't really do any PUFy stuff. PUF manipulation is not entirely deterministic, so the stochastic methods used to convert that to determinism are hidden within the bowels the ChipDNA thing. The security concept is that the PUF holds the SHA3 secret, which is simply a truly random (but fixed) bit sequence. The 'secret' can be an ...

2

To implement challenge-response in ROM only (no computations), you basically need a lookup table, a mapping from challenges to responses. So for a $k$ bit challenge, you would need $2^k$ entries in your lookup table. How would this work on a PUF? Consider the following PUF example (taken from Improved Ring Oscillator PUF: An FPGA-friendly Secure Primitive, ...

1

By the definition of the next bit test any adversary (ML or not) able to guess the next bit of the output with probability non-negligibly greater than 50% is a break. So 60% is horribly broken. Pretty much all "T"RNGs are horribly broken, they should only be used as entropy sources for CSPRNGs. It's also a bad acronym since it's a (meaningless) matter of ...

1

No we still idealistically target 50% inter hamming distance for PUFs, but being probabilistic and cumulative it's not set in stone. It's just that you achieve 100% material efficiency at 50%. Or you can use the Jaccard index which should tend to zero, as in the variance of sets A and B :- I can't find many academic papers that claim a successful PUF ...

1

note: I am unsure that you can get an answer for your question as there's not enough technical information in the paper to reproduce (for me anyway) the results. However, you could work through it in the following method for any ring oscillator. A ring oscillator is comprised of a ring built of an odd number of inverters. The simplest model of this ...

1

You're right about hardware activation devices for desktop applications. Dangling dongles outa your printer port is quite legacy. New applications tend to use some form of on-line activation system. You see this in games and Windows. But it is becoming more common in the embedded world, where it can act as product key, hardware ID, or activation number. ...

1

Strong SRAM PUFs exist, and this is the way a strong PUF device is designed. The challenge (for response) is the access pattern. SRAM tends to be contiguous, so partitioning into CRPs can be easy if the dependability of the silicon is good. This may not always be the case as it is die /family dependent. So you can segment your 64KB into say two units. The "...

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Does it mean that the response is only derived from the content of the SRAM in an uninitialized state? For the raw RAM-PUF response, that's my understanding. How that is turned into a stable value (in practice identical across power-up cycles) is more complex, and requires long-term storage like conventional Flash for associated error-correction data (which ...

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Caveat: my understanding of Physically Unclonable Functions is partial, and my limited exposure to would-be PUF systems is old. I offer a tentative current opinion, hopping there will be constructive contradiction, and that I'll learn something new. I know no practical system (or credible blueprint for such) where possession of a PUF can be assimilated to ...

1

I believe Roel Maes gives a very good answer to your question in his PhD thesis, pages 20-23. In essence, ideally, you need to calculate an array of the Hamming Distance between every pair of responses to the same challenge. Those pairs correspond to either the same chip or different chips depending on if you are looking at intra- or inter- distance. Both ...

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