Paper reading notes in the direction of Web 3.
Bitcoin, BlockStack, and Ethereum White Paper can all be found in Mit 6.824 .
Article Directory
Bitcoin: A Peer-to-Peer Electronic Cash System
propose
Digital signatures can meet the requirements of "direct transactions between online parties without going through a third-party economic institution", but cannot prevent the double-spending problem. At the same time, the digital currency of the intermediary organization cannot conduct irreversible transactions, and at the same time needs to pay intermediate fees.
Double-spending refers to the risk that a cryptocurrency may be spent two or more times. Transaction information within the blockchain can be changed if certain conditions are met.
In order to solve these problems, a peer-to-peer scheme is proposed, through the hash of the network timestamp, forming a record that cannot be changed without proof. The longest chain is not only used as a proof of transaction, but also comes from the largest pool of CPU computing power.
trade
In addition to the transaction system shown in the figure below, a consensus system is required to allow most nodes to agree that each transaction is the first arriving node.
timestamp server
The initial idea was to take a timestamped hash with a large number of items and publish it.
Establishing a distributed timestamp server requires the use of a proof-of-work system similar to Hashcash, which uses the CPU to calculate certain hash values of previous transactions.
The transaction process is as follows:
1) The new transaction is broadcast to all nodes.
2) Each node collects new transactions into blocks.
3) Each node finds a proof of work for this block.
4) When a node finds a proof of work, it broadcasts the block to all nodes
5) A node accepts a block only if all transactions are valid and unspent
6) Nodes create a chain by using the hash of the accepted block as the previous hash to express acceptance of the block in the next block in
Incentives
The first transaction in a block is a special transaction that starts a new coin owned by the creator of the block. This increases the incentive for nodes to support the network and provides a way to distribute coins to issuance as there is no central authority issuing them. A steadily increasing amount of new coins is similar to gold mining miners expending resources to increase circulating gold. In this case, the time and electricity spent are the costs.
space recycling
Blockchain uses Merkle Tree to store transaction records, so past transaction records can be discarded to save space.
privacy level
Through the anonymity of the public key, the information flow of the blockchain can be interrupted to achieve privacy protection.
PBFT- semi-synchronous algorithm
MyTumbler - asynchronous consensus algorithm