  Development of physical cryptographic primitives for generating strong
security keys is central to combating security threats such as counterfeiting
and unauthorized access to electronic devices. We introduce a new class of
physical cryptographic primitives from layered molybdenum disulfide (MoS2)
which leverages the unique properties of this material system. Using chemical
vapor deposition, we synthesize a MoS2 monolayer film covered with speckles of
multilayer islands, where the growth process is engineered for an optimal
speckle density. The physical cryptographic primitive is an array of 2048
pixels fabricated from this film. Using the Clark-Evans test, we confirm that
the distribution of islands on the film exhibits complete spatial randomness,
making this cryptographic primitive ideal for security applications. A unique
optical response is generated by applying an optical stimulus to the structure.
The basis for this unique response is the dependence of the photoemission on
the number of MoS2 layers which by design is random throughout the film. The
optical response is used to generate cryptographic keys. Standard security
tests confirm the uniqueness, reliability, and uniformity of these keys. This
study reveals a new opportunity for generating strong and versatile
nano-engineered security primitives from layered transition metal
dichalcogenides.
