QKD WIP

chapter-qkd/chapter.tex

@@ -167,6 +167,33 @@ improvement in today's hardware.
 
 \section{Securing QKD Networks with Inertial HSMs}
 
+As we discussed above, when it comes down to practical, end-to-end security properties, Quantum Key Distribution
+removes trust in the hardness of particular mathematical problems (good!), but increases trust in the physical
+integrity of the transceivers of the QKD link (bad!). In scenarios where the communicating parties are all located
+within physical proximity, in QKD meaning within at most a few hundred kilometers from each other depending on secret
+key rate requirements, this added trust is of no consequence because the communcating parties' hardware must be trusted
+in either QKD-assisted or purely classical setups. However, this trust requirement becomes a burden as soon as at least
+one party is too far away (or higher secret key rates are required), as now physically trusted relays become necessary.
+
+Extrapolating to practical deployments, we can make two predictions. First, as QKD only solves key distribution, but the
+actual data transfer still happens through normal off-the-shelf telecommunications components in QKD networks, there is
+no reason for a practical QKD setup to \emph{not} also use classical cryptography as an additional layer for defense in
+depth,
+% FIXME citation on defense in depth, and on this hybrid scenario
+meaning the QKD setup will at worst degrade to the same security a purely classical system would provide, never less.
+
+The second prediction we can make is that any practical QKD network will have to use trusted relays to bridge large
+distances. While in certain specialized applications such as the proposed financial QKD network in Swizerland
+% FIXME citation
+smaller, isolated networks are conceivable, in every telecommunication system from the telegraph through the telephone
+system and up to the internet it has been shown conclusively that there is a real demand for a unified, global
+interconnected network. % FIXME citation on historic networks
+
+In this section, we will outline a solution that provides practical, end-to-end security in large-scale QKD networks by
+delegating the hardware trust issue of QKD relays to Inertial Hardware Security Modules. The primary design challenges
+we will address are the systems' overall envelope design, optical passthroughs, and matching the cryptographic
+assumptions behind the IHSM's heartbeat and alarm subsystem to those of the QKD application.
+
 \section{Outlook}
 
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