10个重要的区块链面试问题 *

Bitcoin blocks are not encrypted in any way: Every block is public. What prevents modifications and guarantees data integrity is a value called the block hash. Block content is processed using a special hash function—in the case of Bitcoin, it’s SHA256—and the resulting value is included in the blockchain.

Coins/tokens are used to implement changes between states. 当某人进行交易时, 这是状态的变化, 硬币从一个地址转移到另一个地址. 除此之外, 事务可以包含额外的数据, and a change of state is used to mutate data—the only way to do this in an immutable-by-definition blockchain. 从技术上讲, a blockchain doesn’t need coins for its essential operations, 但是没有他们, some other way needs to be introduced to manage states of the chain and to verify transactions.

当一个新节点启动时, 它对网络一无所知, 因为没有中央服务器. Usually developers provide a list of trusted nodes written directly into the code that can be used for initial peer discovery.

Every full node on the network does block verification. When a new block is announced, every node that receives it does a list of checks. 两个最重要的检查是 工作证明 (if a block provides enough work to be included into chain) and of the validity of all transactions (each transaction must be valid).

scriptPubKey是一种所谓的“锁定脚本”.” It’s found in transaction output and is the encumbrance that must be fulfilled to spend the output.

P2SH is a special type of address where the complex locking script is replaced with its hash. When a transaction attempting to spend the output is presented later, 它必须包含与散列匹配的脚本, 除了解锁脚本.

OP_EQUALVERIFY
scriptPubKey: 1234567 OP_EQUALVERIFY
scriptSig: 1234567

scriptPubKey: "30d" OP_CHECKSEQUENCEVERIFY OP_VERIFY
scriptSig:空

A trapdoor function is a function that is easy to compute in one direction but difficult to compute in the opposite direction unless you have special information. Trapdoor functions are essential for public key encryption—that’s why they are commonly used in blockchain development to represent the ideas of addresses and private keys.

Mining is the process of reaching consensus in blockchain networks. 采矿有两个目的. 首先，它在生成的区块中创建新的硬币. Second, it includes transactions in a distributed ledger by providing 工作证明 to the network; that is, proof that the generated block is valid.

Blocks in the ledger are included in such a way as to build the longest chain, i.e.，累积难度最大的链条. Forking is a situation where there are two candidate blocks competing to form the longest blockchain and two miners discover a solution to the proof-of-work problem within a short period of time from each other. The network is then divided, because some nodes get blocks from miner #1 and some from miner #2.

分叉通常在一个区块中解决, because the probability that this situation happens again gets extremely lower with the next blocks that arise, so soon there is a new longest chain that will be considered as main.

(注意:这种类型的fork不同于 硬叉, which is where some developers decide to create a backward-incompatible change to the blockchain protocol, 从而产生两个永远不同的区块链.)