The increasing convergence of privacy-preserving machine learning and block chain technology has given rise to ground breaking approaches for collaborative model training. This paper meticulously reviews recent advancements in privacy-preserving federated machine learning, with a primary focus on the seamless integration of homomorphic encryption within block chain networks. Delving deep into the intricacies of secure data collaboration, each participant securely maintains their encrypted datasets within the decentralized block chain framework. Our study thoroughly investigates the practical application of homomorphic encryption, carefully examining its computational intricacies and the ongoing efforts in efficiency optimization. Through a comprehensive survey, we critically evaluate the security implications inherent in this integrated framework and present a discourse on potential enhancements to existing cryptographic protocols. The synthesis of our findings aims to contribute nuanced visions into the present state-of-the-art practices, illuminating the challenges faced, and proposing directions for future advancements in privacy-conscious collaborative machine learning within the dynamic context of block chain environments. This research serves as a foundational exploration of the symbiotic relationship between privacy-preserving techniques and block chain, offering valuable guidance for researchers, and others in the field.