  The field of device-independent (DI) quantum information processing concerns
itself with devising and analysing protocols, such as quantum key distribution,
without referring to the quality of the physical devices utilised to execute
the protocols. Instead, the analysis is based on the observed correlations that
arise during a repeated interaction with the devices and, in particular, their
ability to violate the so called Bell inequalities.
  Since the analysis of DI protocols holds irrespectively of the underlying
physical device, it implies that any device can be used to execute the
protocols: If the apparatus is of poor quality, the users of the protocol will
detect it and abort; otherwise, they will accomplish their goal. This strong
statement comes at a price-- the analysis of DI protocols is, a priori,
extremely challenging.
  The thesis presents an approach that can be taken to simplify the analysis of
DI information processing protocols. The idea is the following: Instead of
analysing the most general device leading to the observed correlations, one
should first analyse a significantly simpler device that, in each interaction
with the user, behaves in an identical way, independently of all other
interactions. We call such a device an independently and identically
distributed (IID) device. As the next step, special techniques are used to
prove that, without loss of generality, the analysis of the IID device implies
similar results for the most general device. These are termed reductions to
IID.
  We present two mathematical techniques that can be used as reductions to IID
in the DI setting, each accompanied by a showcase-application that exemplifies
the reduction's usage and benefits. Performing the analysis via a reduction to
IID leads to simpler proofs and significant quantitive improvements, matching
the tight results proven when analysing IID devices.
