- Timestamp Server
The solution we propose begins with a timestamp server. A timestamp server works by taking a hash of a block of items to be timestamped and widely publishing the hash, such as in a newspaper or Usenet post [2-5]. The timestamp proves that the data must have existed at the time, obviously, in order to get into the hash. Each timestamp includes the previous timestamp in its hash, forming a chain, with each additional timestamp reinforcing the ones before it.
timestamp server 時(shí)間戳服務(wù)器
additional 額外的
reinforce 加強(qiáng)
- Proof-of-Work
To implement a distributed timestamp server on a peer-to-peer basis, we will need to use a proof-of-work system similar to Adam Back's Hashcash [6], rather than newspaper or Usenet posts. The proof-of-work involves scanning for a value that when hashed, such as with SHA-256, the hash begins with a number of zero bits. The average work required is exponential in the number of zero bits required and can be verified by executing a single hash.
similar to 與......相似
rather than 而不是
scanning 掃描
a number of 一些
exponential 冪數(shù)的
For our timestamp network, we implement the proof-of-work by incrementing a nonce in the block until a value is found that gives the block's hash the required zero bits. Once the CPU effort has been expended to make it satisfy the proof-of-work, the block cannot be changed without redoing the work. As later blocks are chained after it, the work to change the block would include redoing all the blocks after it.
increment 遞增
nonce 隨機(jī)數(shù)
The proof-of-work also solves the problem of determining representation in majority decision making. If the majority were based on one-IP-address-one-vote, it could be subverted by anyone able to allocate many IPs. Proof-of-work is essentially one-CPU-one-vote.
determining representation 表決
decision making 決策
one-IP-address-one-vote 一個(gè)IP一票
subvert 打倒
allocate 分配
one-CPU-one-vote 一個(gè)CPU一票
The majority decision is represented by the longest chain, which has the greatest proof-of-work effort invested in it. If a majority of CPU power is controlled by honest nodes, the honest chain will grow the fastest and outpace any competing chains. To modify a past block, an attacker would have to redo the proof-of-work of the block and all blocks after it and then catch up with and surpass the work of the honest nodes.
catch up 趕上
surpass 超過(guò)
We will show later that the probability of a slower attacker catching up diminishes exponentially as subsequent blocks are added.
diminish 減少
exponentially 成倍地
subsequent 連串的
To compensate for increasing hardware speed and varying interest in running nodes over time, the proof-of-work difficulty is determined by a moving average targeting an average number of blocks per hour. If they're generated too fast, the difficulty increases.
compensate 補(bǔ)償
vary 改變
interest 利息
over time 隨著時(shí)間的推移
