const crypto = require('crypto')
var Rsa = require('node-rsa')
Encryption libs -- ursa
https://github.com/JoshKaufman/ursa
https://coolaj86.com/articles/asymmetric-public--private-key-encryption-in-node-js/
https://www.npmjs.com/package/ursa
Encryption libs -- rsa
https://github.com/rzcoder/node-rsa
State Channels
http://www.jeffcoleman.ca/state-channels/
https://blog.stephantual.com/what-are-state-channels-32a81f7accab
function hash(obj){
const text = typeof obj == 'string' ? obj : JSON.stringify(obj)
const hash = crypto.createHash('sha256')
hash.update(text)
return hash.digest('hex')
}
function expectString(obj){
if( typeof obj != 'string' ) throw new Error("Expected string")
}
class Wallet {
constructor(){
this.privateKey = new Rsa({b:1024})
this.publicKey = new Rsa()
this.publicKey.importKey( this.privateKey.exportKey("pkcs8-public-pem") , 'public')
}
encrypt(txt){
return this.privateKey.encryptPrivate(txt, 'base64')
}
decrypt(base64){
return this.publicKey.decryptPublic(base64, 'utf8')
}
}
class StateChain {
constructor(publicKeyA,publicKeyB){
this.publicKeyA = publicKeyA
this.publicKeyB = publicKeyB
this.states = []
}
pushState(state){
this.states.push(state)
}
get lastEncryptedHash(){
return this.encryptedHash(this.states.length - 1)
}
encryptedHash(i){
return hash(this.states[i].e)
}
get lastState(){
return this.states[ this.states.length - 1 ]
}
verifyLastState(verbose=false){
if (verbose) console.log("Verifying state "+(this.states.length - 1))
this.verify( this.lastState, verbose )
}
verifyAll(verbose=false){
if (verbose) console.log("verifying all states:")
for(const i in this.states){
const state = this.states[i]
if (!this.verify(state,verbose)) return false
if(state.s.seqnum!=i){
if (verbose) console.log("state sequence is wrong")
if (verbose) console.log(state.s)
return false
}
if(state.s.seqnum==0){
if(state.s.prev!=""){
if (verbose) console.log("state[0] should have empty prev field")
if (verbose) console.log(state.s)
return false
}
}else{
if(state.s.prev!=this.encryptedHash(i-1)){
if (verbose) console.log("stateprev link does not match previous state")
if (verbose) console.log(state.s)
return false
}
}
}
return true
}
verify(state,verbose=false){
return state.verify(this.publicKeyA,this.publicKeyB,verbose)
}
}
class State {
constructor(s,eA,eB){
this.s = s
this.eA = eA
this.eB = eB
}
get e(){
return [this.eA,this.eB]
}
verify(keyA,keyB,verbose=false){
console.log(this)
const hA = keyA.decryptPublic(this.eA,'utf8')
const hB = keyB.decryptPublic(this.eB,'utf8')
const h = hash(this.s)
if (hA != hB){
if (verbose) console.log("The signature of A and B is different.")
return false
}
if (hA != h){
if (verbose) console.log("The signature of A is not the signature of the state.")
return false
}
if (hB != h){
if (verbose) console.log("The signature of B is not the signature of the state.")
return false
}
if (hA == hB && hB == h){
if (verbose) console.log("The state is validated by the signatures of both A and B!")
if (verbose) console.log(this.s)
return true
}
return false // this shouldn't happen -- put exception here
}
}
const playerA = new Wallet()
const playerB = new Wallet()
let chain = new StateChain(playerA.publicKey,playerB.publicKey)
const s0 = {
seqnum:0,
prev:"",
data:{
nextPlayer: "X",
winner: "",
board: [
['-','-','-'],
['-','-','-'],
['-','-','-'],
]
}
}
const h0 = hash(s0)
chain.pushState( new State(s0,playerA.encrypt(h0),playerB.encrypt(h0)) )
chain.verifyLastState(true)
const s1 = {
seqnum:1,
prev:chain.lastEncryptedHash,
data:{
nextPlayer: "O",
winner: "",
board: [
['-','-','-'],
['-','-','X'],
['-','-','-'],
]
}
}
const h1 = hash(s1)
chain.pushState( new State(s1,playerA.encrypt(h1),playerB.encrypt(h1)) )
chain.verifyLastState(true)
const s2 = {
seqnum:2,
prev:chain.lastEncryptedHash,
data:{
nextPlayer: "X",
winner: "",
board: [
['-','-','-'],
['-','O','X'],
['-','-','-'],
]
}
}
const h2 = hash(s2)
chain.pushState( new State(s2,playerA.encrypt(h2),playerB.encrypt(h2)) )
chain.verifyLastState(true)
chain.verifyAll(true)
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