Agriculture, the foundation of human civilization, is undergoing a dramatic transformation driven by the Internet of Things (IoT). IoT devices enable farmers to boost yields, reduce waste, and guarantee a safer and more sustainable food supply chain through everything from accurate crop health monitoring to resource optimization and improved food traceability. However, there are serious risks of illegal access, data manipulation, and privacy violations as data moves through cloud-based platforms. These weaknesses may result in poor decision-making, financial damage, and hazards to the safety of food. Blockchain technology is revolutionary because it offers a decentralized, secure foundation for protecting agricultural data. Together with more sophisticated cryptographic methods like homomorphic encryption and zero-knowledge proofs, it forms a strong framework for guaranteeing data security and privacy. This chapter explores how blockchain and cryptography might be combined to address these pressing problems, providing innovative solutions including safe data storage, decentralized sharing systems, and smart contracts that facilitate effective and transparent transactions. We offer a thorough examination of the most recent developments and enduring difficulties in agricultural data management by classifying blockchain applications and investigating fundamental components including consensus mechanisms and cryptography tools. We show how blockchain technology may transform agriculture, from enhancing the traceability of the food supply chain to resolving the issues of unreliable stakeholders. This chapter also emphasizes the broader potential of these technologies, showcasing their scalability to other domains and their capacity to drive innovation in sustainable resource management and data security.