trust is a very strong and unjustified assumption. For instance, Eve could modify a chip, or infect the software with malware, to make it fail at a crucial time, or to hide a backdoor in say Alice’s unit CP$_{\rm A}$ that leaks the final key, $k_{{\rm A}i}$, generated in say the $i$-th QKD run to her [@military1; @military2]. Due to the complexity and fabrication costs of current chips, these devices are typically designed by different parties, manufactured by an external foundry, and packaged and distributed by separate companies. This gives Eve multiple opportunities to meddle with the hardware. More importantly, hardware Trojans can be very hard to detect in practice. This is so because even slight adjustments to the electrical properties of a few transistors (from the billions of them contained in today’s chips) could already compromise the security. Also, Eve could easily bypass post-fabrication tests by crafting attack triggers that require a sequence of unlikely events, or by altering only a subset of the chips in question [@covert2b; @covert2c]. Similar arguments apply as well to software malware. This shows the weaknesses of the classical post-processing units. We refer the reader to the caption of Fig. \[mem\_att\] for the meaning 