A coin is a chain of transaction records, where each record represents each time an owner transferred the coin to a new owner as payment.

  • The latest transaction record in the chain shows the coin's current owner.

Each coin owner has a public/private key pair which the network uses to verify the integrity of transactions.

When the current owner of a coin wants to transfer the coin to a new owner, they create a transaction record which contains:

  • The public key of the coin's new owner.
  • A hash of the previous transaction record in the chain.
  • A signature of the above hash signed with the current owner's private key.

This information allows the new owner to verify that it received the coin from the right owner.

The Bitcoin Blockchain

Each block of the blockchain is identified with a hash and contains:

  • The hash of the previous block in the chain.
  • A set of transactions.
  • A nonce

When you make a payment, the payee won't accept it until the transaction is in the blockchain.

  • since all transactions are in the blockchain, the payee will find out if the coin has been spent before.

Adding a block to the blockchain (ie. mining)

When a peer receives new transactions, it collects them into a block. Before it can add the block to the blockchain, it needs to do actual CPU work (called proof-of-work).

The process of finding the nonce is calling mining

It takes 10 minutes on average for a peer to mine a new block, which means that the parties involved in a transaction have to wait for about 10 minutes before it appears on the blockchain.

  • A peer broadcasts a block to all peers after finding its proof of work.

E Resources