Web 3方向的论文阅读笔记。
Bitcoin、BlockStack、Ethereum White Paper三篇均可以从Mit 6.824中找到。
Bitcoin: A Peer-to-Peer Electronic Cash System
提出
数字签名能够满足“在线的双方直接交易而不通过第三方的经济机构”的要求，但是无法防止double-spending的问题。同时，中间机构数字货币不能进行不可逆的交易，同时需要支付中间费用。
double-spending是指加密货币可能被使用两次或两次以上的风险。如果满足特定条件，区块链内的交易信息可以更改。
为了解决这些问题，提出了一种点对点的方案，通过网络时间戳的哈希，形成一种如果没有证明则无法被更改的记录。最长的链不仅仅作为交易证明，而且来自于最大CPU算力池。
交易
除了下图所示的交易系统之外，需要一个共识系统，让大多数节点认同每笔交易是第一次到达的节点。
时间戳服务器
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 recovery
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