The 5 requirements for Hash algorithms

• One way
• Deterministic
• Fast computation
• The Avalanche Effect
• Must withstand collisions

P2P Network

• A hacker can only take over the network if they tampered more than 50% of the blockchain nodes at the same time and in a very short time.
• The more nodes there is in the blockchain, it's more difficult to hack the blockchain.
• The blockchain will constantly check if there is invalid blocks and copy it over to the valid ones. → auto update the chain to valid blocks.
• This is how the blockchain brings trust to a trustless environment.

Previous Hash

• Previous hashes creates a cryptographic link between blocks.

Block Nonce

• Block number + Data + Previous hash + Nonce (vary) = Hash