8. Simplified Payment Verification
It is possible to verify payments without running a full network node. A user only needs to keep a copy of the block headers of the longest proof-of-work chain, which he can get by querying network nodes until he's convinced he has the longest chain, and obtain the Merkle branch linking the transaction to the block it's timestamped in. He can't check the transaction for himself, but by linking it to a place in the chain, he can see that a network node has accepted it, and blocks added after it further confirm the network has accepted it.
在不运行完整网络节点的情况下，也能够对支付进行检验。一个用户需要保留最长的工作量证明链条的区块头的拷贝，它可以不断向网络发起询问，直到它确信自己拥有最长的链条，并能够通过梅克尔树(Merkle tree)的分支通向它被加上时间戳并纳入区块的那次交易。节点想要自行检验该交易的有效性原本是不可能的，但通过追溯到链条的某个位置，它就能看到某个节点曾经接受过它，并且于其后追加的区块也进一步证明全网曾经接受了它。
As such, the verification is reliable as long as honest nodes control the network, but is more vulnerable if the network is overpowered by an attacker. While network nodes can verify transactions for themselves, the simplified method can be fooled by an attacker's fabricated transactions for as long as the attacker can continue to overpower the network. One strategy to protect against this would be to accept alerts from network nodes when they detect an invalid block, prompting the user's software to download the full block and alerted transactions to confirm the inconsistency. Businesses that receive frequent payments will probably still want to run their own nodes for more independent security and quicker verification.
当此情形，只要诚实的节点控制了网络，检验机制就是可靠的。但是，当全网被一个计算力占优的攻击者攻击时，将变得较为脆弱。因为网络节点能够自行确认交易的有效性，只要攻击者能够持续地保持计算力优势，简化的机制会被攻击者焊接的交易欺骗。那么一个可行的策略就是，只要他们发现了一个无效的区块，就立刻发出警报，收到警报的用户将立刻开始下载被警告有问题的区块或交易的完整信息，以便对信息的不一致进行判定。对于日常会发生大量收付的商业机构，可能仍会希望运行他们自己的完整节点，以保持较大的独立完全性和检验的快速性。
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