From 9f133a92d0853102863b77dd7c884d1462cf73a4 Mon Sep 17 00:00:00 2001
From: obscuren <geffobscura@gmail.com>
Date: Wed, 8 Jan 2014 23:41:03 +0100
Subject: [PATCH] First dagger impl

---
 dagger.go | 110 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 110 insertions(+)
 create mode 100644 dagger.go

diff --git a/dagger.go b/dagger.go
new file mode 100644
index 0000000000..750a781b04
--- /dev/null
+++ b/dagger.go
@@ -0,0 +1,110 @@
+package main
+
+import (
+  "math/big"
+  "fmt"
+  "math/rand"
+  "time"
+  "github.com/obscuren/sha3"
+)
+
+type Dagger struct {
+  hash *big.Int
+  xn *big.Int
+}
+
+func (dag *Dagger) Search(diff *big.Int) *big.Int {
+  dag.hash = big.NewInt(0)
+
+  obj := BigPow(2, 256)
+  obj = obj.Div(obj, diff)
+
+  fmt.Println("diff", diff, "< objective", obj)
+
+  r := rand.New(rand.NewSource(time.Now().UnixNano()))
+  rnd := big.NewInt(r.Int63())
+  fmt.Println("init rnd =", rnd)
+
+  for i := 0; i < 1000; i++ {
+    if dag.Eval(rnd).Cmp(obj) < 0 {
+      fmt.Println("Found result! i = ", i)
+      return rnd
+    }
+
+    rnd = rnd.Add(rnd, big.NewInt(1))
+  }
+
+  return big.NewInt(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(d.Sum(nil))
+    pk := b.Uint64() & ((1 << ((L - 1) * 3)) - 1)
+    sha.Write(dag.Node(L - 1, pk).Bytes())
+  }
+
+  ret.SetBytes(sha.Sum(nil))
+
+  return ret
+}
+
+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) {
+      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(d.Sum(nil))
+      pk := (b.Uint64() & 0x1ffffff)
+
+      sha.Write(dag.Node(9, pk).Bytes())
+      doneChan <- true
+    }(k)
+  }
+
+  for k := 0; k < 4; k++ {
+    <- doneChan
+  }
+
+  return ret.SetBytes(sha.Sum(nil))
+}