Fraunhofer-Institut für Angewandte und Integrierte Sicherheit AISEC

Filters

2
2 2 2
2
Reset filters

Settings
Now showing 1 - 2 of 2
  • Publication
    A measurement system for capacitive PUF-based security enclosures
    ( 2018)
    Obermaier, J.
    ;
    Immler, V.
    ;
    Hiller, M.
    ;
    Sigl, G.
    Battery-backed security enclosures that are permanently monitored for penetration and tampering are common solutions for providing physical integrity to multi-chip embedded systems. This paper presents a well-tailored measurement system for a batteryless PUF-based capacitive enclosure. The key is derived from the PUF and encrypts the underlying system. We present a system concept for combined enclosure integrity verification and PUF evaluation. The system performs differential capacitive measurements inside the enclosure by applying stimulus signals with a 180° phase shift that isolate the local variation in the femtofarad range. The analog circuitry and corresponding digital signal processing chain perform precise PUF digitization, using a microcontroller-based digital lock-in amplifier. The system's measurement range is approximately ±73 fF, the conversion time per PUF node is less than 0.6 ms, and the raw data shows a measurement noise of 0.3 fF. This is the base for a high-entropy key generation while enabling a short system startup time. The system is scalable to the enclosure size and has been experimentally verified to extract information from 128 PUF nodes, using a system prototype. The results show that our concept forms a cornerstone of a novel batteryless PUF-based security enclosure.
  • Publication
    Take a moment and have some t: Hypothesis testing on raw PUF data
    ( 2017)
    Immler, V.
    ;
    Hiller, M.
    ;
    Obermaier, J.
    ;
    Sigl, G.
    Systems based on PUB derive secrets from physical variation and it is difficult to measure the security level of the obtained PUF response bits in practice. We evaluate raw NW data to assess the quality of the physical source to detect undesired imperfections in the circuit to provide feedback for the PUF designer and improve the achieved security level. Complementing previous work on correlations across a PUF structure, we apply Welch's t-test to quantify the indistinguishability between distributions of different PUF responses, i.e., the values from on-chip locations measured across multiple devices. The threshold levels of the t-test depend on the number of evaluated PUF cells and the desired confidence of the hypothesis test. These t-values are computed from the statistical moments, such as mean and variance, of the tested distributions and indicate if they were not drawn from the same source. We identify that the quantization of the raw PUF data evaluates different statistical moments. Therefore, it is important to evaluate the indistinguishability of the raw PIT data concerning the critical moment which is used by the quantizer. To demonstrate the benefits of the presented evaluation method, we apply this test to public, real-world RO PUF data. As result, the designer is given specific information to optimize later processing steps or the underlying PUF structure. Complementing tests of the NIST 800-90b test suite further substantiate the chosen approach.