quorum/dagger.go

package main

import (
  "math/big"
  "fmt"
  "math/rand"
  "time"
  "github.com/obscuren/sha3"
  "hash"
)

type Dagger struct {
  hash *big.Int
  xn *big.Int
}

var Found bool
func (dag *Dagger) Find(obj *big.Int, resChan chan int64) {
  r := rand.New(rand.NewSource(time.Now().UnixNano()))

  for i := 0; i < 1000; i++ {
    rnd := r.Int63()

    if dag.Eval(big.NewInt(rnd)).Cmp(obj) < 0 {
      // Post back result on the channel
      resChan <- rnd
      // Notify other threads we've found a valid nonce
      Found = true
    } else {
      fmt.Printf(".")
    }

    // Break out if found
    if Found { break }
  }

  resChan <- 0
}

func (dag *Dagger) Search(diff *big.Int) *big.Int {
  // TODO fix multi threading. Somehow it results in the wrong nonce
  amountOfRoutines := 1

  dag.hash = big.NewInt(0)

  obj := BigPow(2, 256)
  obj = obj.Div(obj, diff)

  fmt.Println("diff", diff, "< objective", obj)

  Found =  false
  resChan := make(chan int64, 3)
  var res int64

  for k := 0; k < amountOfRoutines; k++ {
    go dag.Find(obj, resChan)
  }

  // Wait for each go routine to finish
  for k := 0; k < amountOfRoutines; k++ {
    // Get the result from the channel. 0 = quit
    if r := <- resChan; r != 0 {
      res = r
    }
  }

  fmt.Println("\n")

  return big.NewInt(res)
}

func DaggerVerify(hash, diff, nonce *big.Int) bool {
  dagger := &Dagger{}
  dagger.hash = hash

  obj := BigPow(2, 256)
  obj = obj.Div(obj, diff)

  return dagger.Eval(nonce).Cmp(obj) < 0
}

func (dag *Dagger) Node(L uint64, i uint64) *big.Int {
  if L == i {
    return dag.hash
  }

  var m *big.Int
  if L == 9 {
    m = big.NewInt(16)
  } else {
    m = big.NewInt(3)
  }

  sha := sha3.NewKeccak224()
  sha.Reset()
  d := sha3.NewKeccak224()
  b := new(big.Int)
  ret := new(big.Int)

  for k := 0; k < int(m.Uint64()); k++ {
    d.Reset()
    d.Write(dag.hash.Bytes())
    d.Write(dag.xn.Bytes())
    d.Write(big.NewInt(int64(L)).Bytes())
    d.Write(big.NewInt(int64(i)).Bytes())
    d.Write(big.NewInt(int64(k)).Bytes())

    b.SetBytes(Sum(d))
    pk := b.Uint64() & ((1 << ((L - 1) * 3)) - 1)
    sha.Write(dag.Node(L - 1, pk).Bytes())
  }

  ret.SetBytes(Sum(sha))

  return ret
}

func Sum(sha hash.Hash) []byte {
  in := make([]byte, 32)
  return sha.Sum(in)
}

func (dag *Dagger) Eval(N *big.Int) *big.Int {
  pow := BigPow(2, 26)
  dag.xn = N.Div(N, pow)

  sha := sha3.NewKeccak224()
  sha.Reset()
  ret := new(big.Int)

  //doneChan := make(chan bool, 3)

  for k := 0; k < 4; k++ {
    //go func(_k int) {
    _k := k
      d := sha3.NewKeccak224()
      b := new(big.Int)

      d.Reset()
      d.Write(dag.hash.Bytes())
      d.Write(dag.xn.Bytes())
      d.Write(N.Bytes())
      d.Write(big.NewInt(int64(_k)).Bytes())

      b.SetBytes(Sum(d))
      pk := (b.Uint64() & 0x1ffffff)

      sha.Write(dag.Node(9, pk).Bytes())
      //doneChan <- true
    //}(k)
  }

  //for k := 0; k < 4; k++ {
  //  <- doneChan
  //}


  return ret.SetBytes(Sum(sha))
}