Explore the world of blockchain consensus mechanisms in this conference talk from GOTO Amsterdam 2018. Delve into the intricacies of decentralized systems, starting with a brief blockchain introduction. Examine the controversial "proof of work" approach used by Bitcoin, evaluating its energy consumption criticisms. Investigate alternative consensus methods, including "proof of stake" and others. Learn about classical consensus, Byzantine failures, and Byzantine fault tolerance. Understand Nakamoto consensus, Bitcoin validation, and the energy implications of blockchain technology. Discover various alternatives like proof of service, proof of capacity, and proof of expiry time. Analyze the assessment problem in blockchain systems and review real-world examples. Gain valuable insights into the challenges and solutions in achieving consensus in blockchain-based systems.