比特币与区块链

生有可恋 2022-07-10

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基于 block chain 的 bitcoin 从 2009 年上线至今已经十来年了。只知道它是一套基于加密算法的系统，但对其并没有太深的认识。我花了一点时间试着去理解它是如何运作的。

2008年11月，一份署名中本聪（satoshi）的论文被发表在网络上，其标题为《比特币：对等网络电子现金系统》（Bitcoin: A Peer-to-Peer Electronic Cash System）。论文中详细描述了如何使用对等网络来创造一种“不需依赖信任的电子交易系统”。2009年1月比特币网络上线，推出了第一个开源的比特币客户端软件，中本聪使用该软件对第一个比特币“区块”（block，又称为创始区块，genesis block）进行“采矿”（mining），并获得了第一批的50个比特币。最初比特币交易的价值由“bitcointalk”论坛上的使用者彼此协商，其中包括以10,000比特币兑换一整个披萨。

以上是来自WiKi的比特币的诞生史。在这里有几个概念需要搞清楚，第一，比特币是基于P2P的。即交易是在用户和用户之间完成的，不需要银行参与。比特币用到的区块链技术，可以理解为类似Git这种分布式文件系统，任何一个人提交的请求都会被所有人收到。而要支持这个系统运行，需要有一套系统来搭建这个P2P网络，于是就出现了挖矿这个概念。对于运行这套系统的程序，被称为挖矿。系统对挖矿者即运行这套程序的机器进行奖励，而主动运行这套系统的人或机器被称为矿工。

那么P2P网络中的人们如何交易呢？这里又多出一个概念叫比特币钱包。而比特币就是放在钱包中的。钱包类似一个收件地址，可以与其他人交易。而比特币就是一串存在钱包中的字符串，当与其他人交易之后会进行扣费处理，交易记录会同步到比特币的所有网络，即被所有人承认。

我们下载一个钱包看看这个过程是怎么执行的。官方的钱包叫 “Bitcoin Core"，在官网可以下载到：

https://bitcoincore.org/en/download/

下载下来的安装包只有 20M 左右，直接安装：

使用默认位置进行安装即可：

安装完成后，首次使用会让选择数据存放目录。这个目录会存放从2009年至今（2022.7）的所有 Block Chain，即所有的交易记录。这个数据量巨大，大概有 460G 。

首次运行会同步区块，过程非常缓慢。

在同步的同时，可以观察一下这个钱包程序的其它功能，比如它有一个命令行的控制台，可以在其中敲命令。

在控制台中输入 help 可以看到命令帮助。从 help 我们可以了解到，这个 bitcoin core 程序不仅仅运行钱包功能，它是一个全功能的，非常复杂。

命令help的内容：

help

== Blockchain ==
getbestblockhash
getblock "blockhash" ( verbosity )
getblockchaininfo
getblockcount
getblockfilter "blockhash" ( "filtertype" )
getblockfrompeer "blockhash" peer_id
getblockhash height
getblockheader "blockhash" ( verbose )
getblockstats hash_or_height ( stats )
getchaintips
getchaintxstats ( nblocks "blockhash" )
getdeploymentinfo ( "blockhash" )
getdifficulty
getmempoolancestors "txid" ( verbose )
getmempooldescendants "txid" ( verbose )
getmempoolentry "txid"
getmempoolinfo
getrawmempool ( verbose mempool_sequence )
gettxout "txid" n ( include_mempool )
gettxoutproof ["txid",...] ( "blockhash" )
gettxoutsetinfo ( "hash_type" hash_or_height use_index )
preciousblock "blockhash"
pruneblockchain height
savemempool
scantxoutset "action" ( [scanobjects,...] )
verifychain ( checklevel nblocks )
verifytxoutproof "proof"


== Control ==
getmemoryinfo ( "mode" )
getrpcinfo
help ( "command" )
logging ( ["include_category",...] ["exclude_category",...] )
stop
uptime


== Mining ==
getblocktemplate ( "template_request" )
getmininginfo
getnetworkhashps ( nblocks height )
prioritisetransaction "txid" ( dummy ) fee_delta
submitblock "hexdata" ( "dummy" )
submitheader "hexdata"


== Network ==
addnode "node" "command"
clearbanned
disconnectnode ( "address" nodeid )
getaddednodeinfo ( "node" )
getconnectioncount
getnettotals
getnetworkinfo
getnodeaddresses ( count "network" )
getpeerinfo
listbanned
ping
setban "subnet" "command" ( bantime absolute )
setnetworkactive state


== Rawtransactions ==
analyzepsbt "psbt"
combinepsbt ["psbt",...]
combinerawtransaction ["hexstring",...]
converttopsbt "hexstring" ( permitsigdata iswitness )
createpsbt [{"txid":"hex","vout":n,"sequence":n},...] [{"address":amount,...},{"data":"hex"},...] ( locktime replaceable )
createrawtransaction [{"txid":"hex","vout":n,"sequence":n},...] [{"address":amount,...},{"data":"hex"},...] ( locktime replaceable )
decodepsbt "psbt"
decoderawtransaction "hexstring" ( iswitness )
decodescript "hexstring"
finalizepsbt "psbt" ( extract )
fundrawtransaction "hexstring" ( options iswitness )
getrawtransaction "txid" ( verbose "blockhash" )
joinpsbts ["psbt",...]
sendrawtransaction "hexstring" ( maxfeerate )
signrawtransactionwithkey "hexstring" ["privatekey",...] ( [{"txid":"hex","vout":n,"scriptPubKey":"hex","redeemScript":"hex","witnessScript":"hex","amount":amount},...] "sighashtype" )
testmempoolaccept ["rawtx",...] ( maxfeerate )
utxoupdatepsbt "psbt" ( ["",{"desc":"str","range":n or [n,n]},...] )


== Util ==
createmultisig nrequired ["key",...] ( "address_type" )
deriveaddresses "descriptor" ( range )
estimatesmartfee conf_target ( "estimate_mode" )
getdescriptorinfo "descriptor"
getindexinfo ( "index_name" )
signmessagewithprivkey "privkey" "message"
validateaddress "address"
verifymessage "address" "signature" "message"


== Wallet ==
abandontransaction "txid"
abortrescan
addmultisigaddress nrequired ["key",...] ( "label" "address_type" )
backupwallet "destination"
bumpfee "txid" ( options )
createwallet "wallet_name" ( disable_private_keys blank "passphrase" avoid_reuse descriptors load_on_startup external_signer )
dumpprivkey "address"
dumpwallet "filename"
encryptwallet "passphrase"
getaddressesbylabel "label"
getaddressinfo "address"
getbalance ( "dummy" minconf include_watchonly avoid_reuse )
getbalances
getnewaddress ( "label" "address_type" )
getrawchangeaddress ( "address_type" )
getreceivedbyaddress "address" ( minconf include_immature_coinbase )
getreceivedbylabel "label" ( minconf include_immature_coinbase )
gettransaction "txid" ( include_watchonly verbose )
getunconfirmedbalance
getwalletinfo
importaddress "address" ( "label" rescan p2sh )
importdescriptors "requests"
importmulti "requests" ( "options" )
importprivkey "privkey" ( "label" rescan )
importprunedfunds "rawtransaction" "txoutproof"
importpubkey "pubkey" ( "label" rescan )
importwallet "filename"
keypoolrefill ( newsize )
listaddressgroupings
listdescriptors ( private )
listlabels ( "purpose" )
listlockunspent
listreceivedbyaddress ( minconf include_empty include_watchonly "address_filter" include_immature_coinbase )
listreceivedbylabel ( minconf include_empty include_watchonly include_immature_coinbase )
listsinceblock ( "blockhash" target_confirmations include_watchonly include_removed )
listtransactions ( "label" count skip include_watchonly )
listunspent ( minconf maxconf ["address",...] include_unsafe query_options )
listwalletdir
listwallets
loadwallet "filename" ( load_on_startup )
lockunspent unlock ( [{"txid":"hex","vout":n},...] persistent )
newkeypool
psbtbumpfee "txid" ( options )
removeprunedfunds "txid"
rescanblockchain ( start_height stop_height )
restorewallet "wallet_name" "backup_file" ( load_on_startup )
send [{"address":amount,...},{"data":"hex"},...] ( conf_target "estimate_mode" fee_rate options )
sendmany "" {"address":amount,...} ( minconf "comment" ["address",...] replaceable conf_target "estimate_mode" fee_rate verbose )
sendtoaddress "address" amount ( "comment" "comment_to" subtractfeefromamount replaceable conf_target "estimate_mode" avoid_reuse fee_rate verbose )
sethdseed ( newkeypool "seed" )
setlabel "address" "label"
settxfee amount
setwalletflag "flag" ( value )
signmessage "address" "message"
signrawtransactionwithwallet "hexstring" ( [{"txid":"hex","vout":n,"scriptPubKey":"hex","redeemScript":"hex","witnessScript":"hex","amount":amount},...] "sighashtype" )
unloadwallet ( "wallet_name" load_on_startup )
upgradewallet ( version )
walletcreatefundedpsbt ( [{"txid":"hex","vout":n,"sequence":n,"weight":n},...] ) [{"address":amount,...},{"data":"hex"},...] ( locktime options bip32derivs )
walletlock
walletpassphrase "passphrase" timeout
walletpassphrasechange "oldpassphrase" "newpassphrase"
walletprocesspsbt "psbt" ( sign "sighashtype" bip32derivs finalize )


== Zmq ==
getzmqnotifications

同时还有流量监控窗口：

同步的数据是基于P2P网络的，可以看到所有节点的信息：

其中主窗口是当前客户端的信息：

试着下载的过程中，频繁报错：

从日志中可以看到进行 block checksum 时失败，此时程序打开就报错，没法再同步。

2022-07-09T04:58:05Z LevelDB read failure: Corruption: block checksum mismatch: D:\Bitcoin\chainstate/004337.ldb
2022-07-09T04:58:05Z Fatal LevelDB error: Corruption: block checksum mismatch: D:\Bitcoin\chainstate/004337.ldb
2022-07-09T04:58:05Z You can use -debug=leveldb to get more complete diagnostic messages
2022-07-09T04:58:05Z Error: Error reading from database, shutting down.
2022-07-09T05:00:13Z Error reading from database: Fatal LevelDB error: Corruption: block checksum mismatch: D:\Bitcoin\chainstate/004337.ldb

网上找到解决方案，进到安装目录，执行 -reindex 重新编译索引：

C:\Users\Administrator>cd d "c:\Program Files"
c:\Program Files>cd Bitcoin
c:\Program Files\Bitcoin>bitcoin-qt.exe -reindex

再次观察 debug.log 文件，可以看到开始重新对下载下来的 blk00xx.dat 进行索引。

2022-07-09T05:01:59Z Loaded 119211 blocks from external file in 37906ms
2022-07-09T05:01:59Z Reindexing block file blk00001.dat...
2022-07-09T05:02:05Z Loaded 11513 blocks from external file in 6416ms
2022-07-09T05:02:05Z Reindexing block file blk00002.dat...
2022-07-09T05:02:10Z Loaded 5810 blocks from external file in 4740ms
2022-07-09T05:02:10Z Reindexing block file blk00003.dat...
2022-07-09T05:02:15Z Loaded 5854 blocks from external file in 4660ms
2022-07-09T05:02:15Z Reindexing block file blk00004.dat...
2022-07-09T05:02:19Z Loaded 6304 blocks from external file in 4934ms
2022-07-09T05:02:19Z Reindexing block file blk00005.dat...
2022-07-09T05:02:25Z Loaded 7308 blocks from external file in 5129ms
2022-07-09T05:02:25Z Reindexing block file blk00006.dat...
...