From 4598fd222a3423bb77f19bdf936cd355cc8c2a08 Mon Sep 17 00:00:00 2001
From: Beaudan <beau@loki.network>
Date: Wed, 31 Oct 2018 16:08:46 +1100
Subject: [PATCH] Cleaned up newNonce stuff. Now doing target calculation with
 BigIntegers

---
 js/modules/loki_message_api.js |  4 +--
 libloki/proof-of-work.js       | 66 +++++++++++++++++-----------------
 2 files changed, 36 insertions(+), 34 deletions(-)

diff --git a/js/modules/loki_message_api.js b/js/modules/loki_message_api.js
index 44d291d5c..283f86bae 100644
--- a/js/modules/loki_message_api.js
+++ b/js/modules/loki_message_api.js
@@ -30,7 +30,7 @@ function initialize({ url }) {
           timestamp,
           ttl,
           pubKey,
-          data,
+          data: Array.from(data),
         });
 
         // Handle child process error (should never happen)
@@ -133,4 +133,4 @@ function HTTPError(message, providedCode, response, stack) {
     e.response = response;
   }
   return e;
-}
\ No newline at end of file
+}
diff --git a/libloki/proof-of-work.js b/libloki/proof-of-work.js
index 1c633e510..fd1057d6a 100644
--- a/libloki/proof-of-work.js
+++ b/libloki/proof-of-work.js
@@ -1,19 +1,22 @@
 const hash = require('js-sha512');
 const bb = require('bytebuffer');
+const BigInteger = require('jsbn').BigInteger;
 
 const NONCE_LEN = 8;
+// Modify this value for difficulty scaling
+const NONCE_TRIALS = 1000;
 
 // Increment Uint8Array nonce by 1 with carrying
 function incrementNonce(nonce) {
   let idx = NONCE_LEN - 1;
-  const newNonce = nonce;
+  const newNonce = new Uint8Array(nonce);
   newNonce[idx] += 1;
   // Nonce will just reset to 0 if all values are 255 causing infinite loop
-  while (nonce[idx] === 0 && idx > 0) {
+  while (newNonce[idx] === 0 && idx > 0) {
     idx -= 1;
     newNonce[idx] += 1;
   }
-  return nonce;
+  return newNonce;
 }
 
 // Convert a Uint8Array to a base64 string
@@ -25,27 +28,27 @@ function bufferToBase64(buf) {
   return bb.btoa(binaryString);
 }
 
-// Convert javascript number to Uint8Array of length 8
-function numberToUintArr(numberVal) {
+// Convert BigInteger to Uint8Array of length NONCE_LEN
+function bigIntToUint8Array(bigInt) {
   const arr = new Uint8Array(NONCE_LEN);
   let n;
   for (let idx = NONCE_LEN - 1; idx >= 0; idx -= 1) {
     n = NONCE_LEN - (idx + 1);
     // 256 ** n is the value of one bit in arr[idx], modulus to carry over
-    arr[idx] = (numberVal / 256**n) % 256;
+    // (bigInt / 256**n) % 256;
+    const uint8Val = (bigInt.divide((new BigInteger('256')).pow(n))).mod(new BigInteger('256'));
+    arr[idx] = uint8Val.intValue();
   }
   return arr;
 }
 
 // Compare two Uint8Arrays, return true if arr1 is > arr2
-function compareUint8Arrays(arr1, arr2) {
+function greaterThan(arr1, arr2) {
   // Early exit if lengths are not equal. Should never happen
   if (arr1.length !== arr2.length)
     return false;
 
-  const len = arr1.length
-
-  for (let i = 0; i < len; i += 1) {
+  for (let i = 0, len = arr1.length; i < len; i += 1) {
     if (arr1[i] > arr2[i])
       return true;
     if (arr1[i] < arr2[i])
@@ -63,40 +66,39 @@ function calcPoW(timestamp, ttl, pubKey, data) {
   const payload = new Uint8Array(leadingArray.length + data.length);
   payload.set(leadingArray);
   payload.set(data, leadingArray.length);
-  // Modify this value for difficulty scaling
-  const nonceTrialsPerByte = 1000;
+
+  // payloadLength + NONCE_LEN
+  const totalLen = (new BigInteger(payload.length.toString())).add(new BigInteger(NONCE_LEN.toString()));
+  // ttl * totalLen
+  const ttlMult = (new BigInteger(ttl.toString())).multiply(totalLen);
+  // ttlMult / (2^16 - 1)
+  const innerFrac = ttlMult.divide((new BigInteger('2').pow(16)).subtract(new BigInteger('1')));
+  // totalLen + innerFrac
+  const lenPlusInnerFrac = totalLen.add(innerFrac);
+  // NONCE_TRIALS * lenPlusInnerFrac
+  const denominator = (new BigInteger(NONCE_TRIALS.toString())).multiply(lenPlusInnerFrac);
+  // 2^64 - 1
+  const two64 = (new BigInteger('2').pow(64)).subtract(new BigInteger('1'));
+  // two64 / denominator
+  const targetNum = two64.divide(denominator);
+  const target = bigIntToUint8Array(targetNum);
+
   let nonce = new Uint8Array(NONCE_LEN);
-  let trialValue = numberToUintArr(Number.MAX_SAFE_INTEGER);
-  // Target is converted to Uint8Array for simple comparison with trialValue
-  const targetNum = Math.floor(2**64 / (
-    nonceTrialsPerByte * (
-      payload.length + NONCE_LEN + (
-        (ttl * ( payload.length + NONCE_LEN )) /
-        2**16
-      )
-    )
-  ));
-  const target = numberToUintArr(targetNum);
+  let trialValue = bigIntToUint8Array(new BigInteger(Number.MAX_SAFE_INTEGER.toString()));
   const initialHash = new Uint8Array(bb.wrap(hash(payload), 'hex').toArrayBuffer());
   const innerPayload = new Uint8Array(initialHash.length + NONCE_LEN);
   innerPayload.set(initialHash, NONCE_LEN);
   let resultHash;
-  while (compareUint8Arrays(trialValue, target)) {
+  while (greaterThan(trialValue, target)) {
     nonce = incrementNonce(nonce);
     innerPayload.set(nonce);
     resultHash = hash(innerPayload);
-    trialValue = (new Uint8Array(bb.wrap(resultHash, 'hex').toArrayBuffer())).slice(0, 8);
+    trialValue = (new Uint8Array(bb.wrap(resultHash, 'hex').toArrayBuffer())).slice(0, NONCE_LEN);
   }
   return bufferToBase64(nonce);
 }
 
 // Start calculation in child process when main process sends message data
 process.on('message', (msg) => {
-  // Convert data back to Uint8Array after IPC has serialised to JSON
-  const msgLen = Object.keys(msg.data).length;
-  const msgData = new Uint8Array(msgLen);
-  for (let i = 0; i < msgLen; i += 1) {
-    msgData[i] = msg.data[i];
-  }
-	process.send({nonce: calcPoW(msg.timestamp, msg.ttl, msg.pubKey, msgData)});
+	process.send({nonce: calcPoW(msg.timestamp, msg.ttl, msg.pubKey, new Uint8Array(msg.data))});
 });