This chapter discusses the reason why we have chosen to study perfectly secure cryptography (as a branch of information-theoretic cryptography) among the existing approaches to cryptography in IoT. To this end, we take a systematic approach. We first introduce timeliness and resource constraint awareness as two critical requirements of cryptography in IoT and highlight the trade-off between them. Next, we use the existing research literature to establish an ecosystem as well as a life cycle for each of the following fields. Real-time cryptographyResource-constrained cryptography (including embedded and lightweight cryptography)Cryptography in IoTReal-time cryptographyResource-constrained (embedded and lightweight) cryptography in IoT In the next step, we demonstrate that all the developed ecosystems and life cycles are closely similar to each other. The ecosystems consist of similar enablers and application areas. Further, the life cycles include similar phases with similar challenges and issues in each phase. These findings lead to the formation of common ecosystems and life cycles for all of the aforementioned fields. Finally, we establish an ecosystem as well as a life cycle for information-theoretic cryptography and highlight their similarities to the common ecosystem and the common life cycle mentioned above. These similarities suggest information-theoretic cryptography as a promising solution for resolving the trade-off between the requirements of cryptography in IoT.