Quality of Service Guarantees for Physical Unclonable Functions

TL;DR

This paper develops methods to ensure reliable, secure, and private key agreement using noisy physical unclonable functions (PUFs), introducing a quality of service parameter to guarantee reliability for a subset of outputs.

Contribution

It proposes a new approach with a quality of service parameter to guarantee reliability for a subset of PUF outputs, improving upon existing methods.

Findings

Reliability guarantees can be provided for a subset of PUF outputs using truncated Gaussian models.

Guaranteeing reliability for all outputs without elimination is impossible without secrecy leakage.

Transform coding combined with scalar quantizers effectively extracts uncorrelated bits from correlated PUF outputs.

Abstract

We consider a secret key agreement problem in which noisy physical unclonable function (PUF) outputs facilitate reliable, secure, and private key agreement with the help of public, noiseless, and authenticated storage. PUF outputs are highly correlated, so transform coding methods have been combined with scalar quantizers to extract uncorrelated bit sequences with reliability guarantees. For PUF circuits with continuous-valued outputs, the models for transformed outputs are made more realistic by replacing the fitted distributions with corresponding truncated ones. The state-of-the-art PUF methods that provide reliability guarantees to each extracted bit are shown to be inadequate to guarantee the same reliability level for all PUF outputs. Thus, a quality of service parameter is introduced to control the percentage of PUF outputs for which a target reliability level can be guaranteed. A public ring oscillator (RO) output dataset is used to illustrate that a truncated Gaussian distribution can be fitted to transformed RO outputs that are inputs to uniform scalar quantizers such that reliability guarantees can be provided for each bit extracted from any PUF device under additive Gaussian noise components by eliminating a small subset of PUF outputs. Furthermore, we conversely show that it is not possible to provide such reliability guarantees without eliminating any PUF output if no extra secrecy and privacy leakage is allowed.