# Evaluating the Efficiency of Physical and Cryptographic Security Solutions for Quantum Immune IoT
## 4 Related Work on Efficiency Simulations  
This subsection presents background information and related work on the simulation approaches for energy efficiency evaluation. The section compares and highlights the advantages of our approach, which will be described in the following section.  
Simulation-based performance and/or power consumption evaluation approaches can be divided into two main categories: full system simulators and single component (e.g., processor, memory) simulators. The full system simulators can be further divided into virtual system approaches based on abstract models of both applications and execution platforms, virtual platform approaches, which simulate executable applications in functional platform models and virtual prototype approaches, which execute real applications in a detailed, low-level platform model. Both virtual platforms and virtual prototypes are instruction accurate, but virtual platforms are typically coarsely timed and fast to simulate, whereas virtual prototypes are highly accurate but require a lot of modeling effort and are slow to simulate. Virtual systems are not instruction accurate but facilitate low modeling effort and high enough precision for early evaluation and design space exploration.  
Our ABSOLUT tool is a virtual system approach where both the security approach as well as different IoT platforms are modeled. It is suitable for cost-effective evaluation of post-quantum solutions as we want to study and compare a large amount of different algorithms and study their feasibility in IoT with a large amount of platforms. Porting all the algorithms to versatile platforms is not a feasible alternative. The simulation speed of ABSOLUT depends on the complexity of the modeled applications and platforms, but the typical range has been between 30 and 300 MOPS. The average simulation error in the case studies, verified with measurements in real hardware, has been 12%.  
Gem5 [50] is an instruction accurate simulation system with configurable component models and speed/accuracy tradeoff capability. The nominal simulation speed varies between 300 KIPS and 3 MIPS. SimuBoost [51] is a method for the parallelization of full system simulation based on a virtual platform. Sniper [52] is a parallel multi-core simulator for the performance and power consumption of x86 architectures. It can achieve up to 2 MIPS simulation performance with at most 25% error. VirtualSoC [53] is a method for the full system simulation of a general purpose CPU and a many-core hardware accelerator using Quick Emulator (QEMU) and SystemC. Virtual system-based approaches have been proposed by [54; 55]. COSSIM [56] is a framework for the full system simulation of networking and processing parts of cyber-physical systems (CPS). It is able to evaluate the performance, power-consumption and security aspects of CPS systems and proposes hardware acceleration with field-programmable gate arrays (FPGAs) to achieve rapid evaluation.  
Quantum immune security approaches have typically been evaluated only by running them on real hardware platforms targeted for desktop or IoT devices. This has enabled development of solutions that are optimized for particular devices and processors. A simulation based approach has been used by one research group [57] who studied how the efficiency of application-specific integrated circuit (ASIC) plans for post-quantum crypto systems can be evaluated using the Bluespec SystemVerilog tool. They evaluated designs of two algorithms (NTRUEncrypt and TTS) and studied their performance in the respect of execution times. Our ABSOLUT simulator approach can be used to evaluate the same solutions of different platforms--from desktop to embedded--and it can be used to receive power consumption and energy efficiency information.