High profile cybersecurity attacks on networks and the occurrences of critical security breaches on existing wireless sensor networks grow by the day. The distributed ledger technology provided for by blockchainwith all its benefits has shown great industrial prospects in the face of the rampant occurrences of cyber thefts of critical data from compromised networks. The centralized identity model relies on centralized authentication mechanisms that create a single point of failure for such database systems. Again, thecentralized data is a honeypot for cyber-attacks.Blockchain as a database structure adopts an authentication mechanism that depends on the distributed ledger technology to eliminate the incidences of single point of failure.Although Blockchain holds security benefits for ensuring enhanced privacy and confidentiality for stored data, the computational overhead in classical blockchain technology makes it a challenge for full use in a network where its devices are resource constrained. In this thesis, solutions have been proposed to solve the aforementioned problems. The main contributions of the PhD thesis are the following: the proposal of a blockchain-based architecture for IoT security, the proposal of cryptographic approaches for securityreinforcement in blockchain-based architectures, and the elaboration of a model based on a formal approach, namely Petri nets, for simulation, analysis and verification of blockchain-based architectures for IoT.