International Association
for Cryptologic Research

We revisit optical physical unclonable functions (PUFs), which were

proposed by Pappu et al. in their seminal first publication on PUFs

[40, 41]. The first part of the paper treats non-integrated optical

PUFs. Their security against modeling attacks is analyzed, and we

discuss new image transformations that maximize the PUF\'s out-

put entropy while possessing similar error correction capacities as

previous approaches [40, 41]. Furthermore, the influence of us-

ing more than one laser beam, varying laser diameters, and smaller

scatterer sizes is systematically studied. Our findings enable the

simple enhancement of an optical PUF\'s security without addi-

tional hardware costs. Next, we discuss the novel application of

non-integrated optical PUFs as so-called \"Certifiable PUFs\". The

latter are useful to achieve practical security in advanced PUF-pro-

tocols, as recently observed by Rührmair and van Dijk at Oakland

2013 [48]. Our technique is the first mechanism for Certifiable

PUFs in the literature, answering an open problem posed in [48].

In the second part of the paper, we turn to integrated optical

PUFs. We build the first prototype of an integrated optical PUF

that functions without moving components and investigate its se-

curity. We show that these PUFs can surprisingly be attacked by

machine learning techniques if the employed scattering structure is

linear, and if the raw interference images of the PUF are available

to the adversary. Our result enforces the use of non-linear scattering

structures within integrated PUFs. The quest for suitable materials is identified as a central, but currently open research problem.

Our work makes intensive use of two prototypes of optical PUFs. The

presented integratable optical PUF prototype is, to our knowledge,

the first of its kind in the literature.