2
How a thin node in network verify the validity of the blockchain tree? I think the node must wait for a time period to get the same valid block from some of its peers.
How a thin node ensures the validity of blockchain?
Answers
3
Most thin clients only download, check and keep the block headers. They do not download the transactions of blocks, so they cannot fully verify blocks.
To learn about transactions they request information from full nodes which will send them a Merkle block for each transaction of interest. With the transaction and the Merkle block, the thin client can verify that the transaction was indeed part of the block. When this transaction gets additional confirmations (i.e. more blocks get found building on the block this transaction was included in), the thin client assumes that the network accepted the block and that the block is valid.
There are also some thin clients that outsource verification to remote services such as mobile wallets of online wallet services.
1I think the term 'thin client' is also used to refer to clients that outsource everything to a remote server. – Pieter Wuille – 2016-12-15T17:08:49.887
Ah yeah, I keep forgetting about mobile wallets of online wallet services like blockchain.info… – Murch – 2016-12-15T17:10:31.820
A thin client wouldn't outsource the safe keeping of private keys no? Whereas a mobile wallet like bc requires you to trust them for the safe keeping of your private key. – renlord – 2016-12-15T21:14:54.230
@renlord: maybe that's the relevant distinction. – Murch – 2016-12-15T22:56:51.373