The different dimensions of applications of IoT have made it to venture in almost every field. The IoT environments are famous since they make use of data collecting devices like sensors. These devices are generally fueled through the use of batteries; hence, they are having lower power and capacities. One of the many challenges that are faced when IoT devices are deployed in practical scenarios is of security. In order to ensure this security, feature many researchers have targeted to use traditional cryptographic concepts; however, they too seem to be not a complete solution. Hence, lightweight cryptography comes to the rescue. Hence, this chapter presents an integration of blockchain and lightweight cryptography for ensuring the safety of IoT environments. It presents the lightweight blockchain architecture that can be deployed in real-world applications in order to secure the systems using IoT.