A Bitcoin Script interpreter and debugger in Scala
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README.md

bitcoin4s

Build Status Coverage Status License: MIT

Scala library for experimenting with Bitcoin scripts. Provides a step by step debugger through REST API. Passes all bitcoin script test cases from bitcoin core.

The code in repository runs the https://nioctib.tech website.

Table of Content

Parse bitcoin script

scala> import it.softfork.bitcoin4s.script.Parser
import it.softfork.bitcoin4s.script.Parser

scala> Parser.parse("0x76a9149984a74e6566b5009d47e46949938337081e9e9888ac")
res0: Seq[it.softfork.bitcoin4s.script.ScriptElement] = List(OP_DUP, OP_HASH160, OP_PUSHDATA(20), ScriptConstant: 0x9984a74e6566b5009d47e46949938337081e9e98, OP_EQUALVERIFY, OP_CHECKSIG)

Run bitcoin script interpreter

The following code would interpret the first input of transaction bac02148041affd9dec93d30a86d1777d9570ab5d36fa2e0b7a20c0fa208e458. It uses the Blockcypher API to fetch transaction information.

scala> :paste
// Entering paste mode (ctrl-D to finish)

import it.softfork.bitcoin4s.Boot
val boot = new Boot {}
import boot._
import it.softfork.bitcoin4s.transaction.TxId
import scala.concurrent.Await
import scala.concurrent.duration._

val txId = TxId("bac02148041affd9dec93d30a86d1777d9570ab5d36fa2e0b7a20c0fa208e458")
val interpretedOutcome = Await.result(blockcypherService.interpret(txId, 0), 10.seconds)

interpretedOutcome.map{ case (finalState@_, interpretedResult) => interpretedResult }

// Exiting paste mode, now interpreting.

...

res0: scala.util.Either[it.softfork.bitcoin4s.script.InterpreterError,Option[Boolean]] = Right(Some(true))

REST API

Running sbt reStart under the project root starts up an HTTP server listening to port 8888 which serves a few REST endpoints.

Example 1:

Execute the unlocking script of the first input of transaction 85db1042f083a8fd6f96fd1a76dc7b8373df9f434979bdcf2432ecf9e0c212ac and its corresponding locking script.

➜ curl localhost:8888/v1/transaction/85db1042f083a8fd6f96fd1a76dc7b8373df9f434979bdcf2432ecf9e0c212ac/input/0/interpret
{
  "result" : {
    "type" : "Result",
    "value" : true
  },
  "state" : {
    "scriptPubKey" : [ {
      "type" : "OP_DUP",
      "value" : 118
    }, {
      "type" : "OP_HASH160",
      "value" : 169
    }, {
      "type" : "OP_PUSHDATA",
      "value" : 20
    }, {
      "type" : "ScriptConstant",
      "value" : "0x9b29f00db6970f2435c5576479cb5a79da56b078"
    }, {
      "type" : "OP_EQUALVERIFY",
      "value" : 136
    }, {
      "type" : "OP_CHECKSIG",
      "value" : 172
    } ],
    "scriptSig" : [ {
      "type" : "OP_PUSHDATA",
      "value" : 72
    }, {
      "type" : "ScriptConstant",
      "value" : "0x30450221009e1def21a903a4122a36052e0e32d3456ba409df0de45677412c31ea440962b4022036543b57869b3228a6d87f578e0014a10119175183140d7803d9949dfc24a89c01"
    }, {
      "type" : "OP_PUSHDATA",
      "value" : 33
    }, {
      "type" : "ScriptConstant",
      "value" : "0x03338efa2d319a07b8487205f5643f709ebe94fedb2b0ce61bbbf04262242b8ad0"
    } ],
    "currentScript" : [ ],
    "stack" : [ {
      "type" : "ScriptNum",
      "value" : 1
    } ],
    "altStack" : [ ],
    "stage" : {
      "type" : "ExecutingScriptPubKey"
    }
  }
}
Example 2

Same example as example 1, but stream each of the execution step back using websocket.

➜ wscat -c ws://localhost:8888/v1/transaction/85db1042f083a8fd6f96fd1a76dc7b8373df9f434979bdcf2432ecf9e0c212ac/input/0/stream-interpret
connected (press CTRL+C to quit)
< {"result":{"type":"NoResult"},"state":{"scriptPubKey":[{"type":"OP_DUP","value":118},{"type":"OP_HASH160","value":169},{"type":"OP_PUSHDATA","value":20},{"type":"ScriptConstant","value":"0x9b29f00db6970f2435c5576479cb5a79da56b078"},{"type":"OP_EQUALVERIFY","value":136},{"type":"OP_CHECKSIG","value":172}],"scriptSig":[{"type":"OP_PUSHDATA","value":72},{"type":"ScriptConstant","value":"0x30450221009e1def21a903a4122a36052e0e32d3456ba409df0de45677412c31ea440962b4022036543b57869b3228a6d87f578e0014a10119175183140d7803d9949dfc24a89c01"},{"type":"OP_PUSHDATA","value":33},{"type":"ScriptConstant","value":"0x03338efa2d319a07b8487205f5643f709ebe94fedb2b0ce61bbbf04262242b8ad0"}],"currentScript":[{"type":"OP_PUSHDATA","value":72},{"type":"ScriptConstant","value":"0x30450221009e1def21a903a4122a36052e0e32d3456ba409df0de45677412c31ea440962b4022036543b57869b3228a6d87f578e0014a10119175183140d7803d9949dfc24a89c01"},{"type":"OP_PUSHDATA","value":33},{"type":"ScriptConstant","value":"0x03338efa2d319a07b8487205f5643f709ebe94fedb2b0ce61bbbf04262242b8ad0"}],"stack":[],"altStack":[],"stage":{"type":"ExecutingScriptSig"}}}
< {"result":{"type":"NoResult"},"state":{"scriptPubKey":[{"type":"OP_DUP","value":118},{"type":"OP_HASH160","value":169},{"type":"OP_PUSHDATA","value":20},{"type":"ScriptConstant","value":"0x9b29f00db6970f2435c5576479cb5a79da56b078"},{"type":"OP_EQUALVERIFY","value":136},{"type":"OP_CHECKSIG","value":172}],"scriptSig":[{"type":"OP_PUSHDATA","value":72},{"type":"ScriptConstant","value":"0x30450221009e1def21a903a4122a36052e0e32d3456ba409df0de45677412c31ea440962b4022036543b57869b3228a6d87f578e0014a10119175183140d7803d9949dfc24a89c01"},{"type":"OP_PUSHDATA","value":33},{"type":"ScriptConstant","value":"0x03338efa2d319a07b8487205f5643f709ebe94fedb2b0ce61bbbf04262242b8ad0"}],"currentScript":[{"type":"OP_PUSHDATA","value":33},{"type":"ScriptConstant","value":"0x03338efa2d319a07b8487205f5643f709ebe94fedb2b0ce61bbbf04262242b8ad0"}],"stack":[{"type":"ScriptConstant","value":"0x30450221009e1def21a903a4122a36052e0e32d3456ba409df0de45677412c31ea440962b4022036543b57869b3228a6d87f578e0014a10119175183140d7803d9949dfc24a89c01"}],"altStack":[],"stage":{"type":"ExecutingScriptSig"}}}
< {"result":{"type":"NoResult"},"state":{"scriptPubKey":[{"type":"OP_DUP","value":118},{"type":"OP_HASH160","value":169},{"type":"OP_PUSHDATA","value":20},{"type":"ScriptConstant","value":"0x9b29f00db6970f2435c5576479cb5a79da56b078"},{"type":"OP_EQUALVERIFY","value":136},{"type":"OP_CHECKSIG","value":172}],"scriptSig":[{"type":"OP_PUSHDATA","value":72},{"type":"ScriptConstant","value":"0x30450221009e1def21a903a4122a36052e0e32d3456ba409df0de45677412c31ea440962b4022036543b57869b3228a6d87f578e0014a10119175183140d7803d9949dfc24a89c01"},{"type":"OP_PUSHDATA","value":33},{"type":"ScriptConstant","value":"0x03338efa2d319a07b8487205f5643f709ebe94fedb2b0ce61bbbf04262242b8ad0"}],"currentScript":[],"stack":[{"type":"ScriptConstant","value":"0x03338efa2d319a07b8487205f5643f709ebe94fedb2b0ce61bbbf04262242b8ad0"},{"type":"ScriptConstant","value":"0x30450221009e1def21a903a4122a36052e0e32d3456ba409df0de45677412c31ea440962b4022036543b57869b3228a6d87f578e0014a10119175183140d7803d9949dfc24a89c01"}],"altStack":[],"stage":{"type":"ExecutingScriptSig"}}}
...
...
< {"result":{"type":"Result","value":true},"state":{"scriptPubKey":[{"type":"OP_DUP","value":118},{"type":"OP_HASH160","value":169},{"type":"OP_PUSHDATA","value":20},{"type":"ScriptContant","value":[-101,41,-16,13,-74,-105,15,36,53,-59,87,100,121,-53,90,121,-38,86,-80,120]},{"type":"OP_EQUALVERIFY","value":136},{"type":"OP_CHECKSIG","value":172}],"scriptSig":[{"type":"OP_PUSHDATA","value":72},{"type":"ScriptContant","value":[48,69,2,33,0,-98,29,-17,33,-87,3,-92,18,42,54,5,46,14,50,-45,69,107,-92,9,-33,13,-28,86,119,65,44,49,-22,68,9,98,-76,2,32,54,84,59,87,-122,-101,50,40,-90,-40,127,87,-114,0,20,-95,1,25,23,81,-125,20,13,120,3,-39,-108,-99,-4,36,-88,-100,1]},{"type":"OP_PUSHDATA","value":33},{"type":"ScriptContant","value":[3,51,-114,-6,45,49,-102,7,-72,72,114,5,-11,100,63,112,-98,-66,-108,-2,-37,43,12,-26,27,-69,-16,66,98,36,43,-118,-48]}],"currentScript":[],"stack":[{"type":"ScriptNum","value":1}],"altStack":[],"stage":{"type":"ExecutingScriptPubKey"}}}
disconnected

Develop nioctib website locally

nioctib.tech website is intended to be a Bitcoin educational site. Right now it supports displaying and debugging Bitcoin transactions at the OpCode level.

Start backend server

In the project root directory, run sbt reStart, it will start the backend web server at the port 8888

Start frontend development server

In the client directory, run yarn install to install neccessary packages, then run yarn run start to start the frontend development server at port 3000. Now the website should be available at http://localhost:3000