Genesis block with the hash block carrying a similar replica of the genesis block. Hash functions: Properties: Blockchain is protected by the properties of hash functions. Decentralisation of the blockchain #Blockchains are based on an active peer 2 peer network which interchanges every single block. Everyone has his own copy of the whole blockchain.  Brute forcing takes a lot of time and resources... changing one thing will result in a different result and you will be able to pick up the change. Orphan blocks & mem pools. where transactions on the blockchain are verified. High fees is what the miners carry out first. Hash's and infeasability... having to crack a number of hash's to change a transaction.

Essential Components of Blockchain Blockchain uses: Smart contracts, data immutability, currency, naming systems, NFT's  Smart contract compared to AWS... they act as a computer Consensus; each computer agrees on the order and contents of date being processed, determine when the agreement has been reached. *Not always instant. #Consensus Algorithms... Blockchains have a finite capacity... memory CPU disk & bandwidth