Side-channel attacks (SCA) enable attackers to gain access to non-disclosed information by measuring emissions of a system, e.g., timing, electromagnetic waves or power consumption. The emissions of a system can typically only be measured on the final system. As a consequence, the analysis of such security threats is often only possible at a very late stage in the development process. In this paper, we present an approach to simulate timing attacks in early stages of the development process with SystemC and discuss the potentials and limitations of this approach. Our results show that the simulation of SCA in SystemC is generally possible, but currently difficult due to an explanation gap. It is, to the best of our knowledge, not well understood where the causal connection between physical quantities and data, which is exploited in SCA, comes from. This poses a major challenge for the design of precise models that accurately reflect physical insights for early security analysis.