blockchain_add_pow.ipynb

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      "start to miner first block time :1524652057.52226\n",
      "miner first block time completed,used 2.3928141593933105s\n",
      "start to miner first block time :1524652059.915224\n",
      "miner second block time completed,used 1.791139841079712s\n",
      "\n",
      "print block info ####:\n",
      "\n",
      "\n",
      "\n",
      "{'index': 0, 'timestamp': '01/01/2018', 'data': 'genesis block', 'previousHash': '', 'nonce': 0, 'hash': '1fb6344a6e5c8f0c7e03e1ded0e831a3d92c3741eb5f7153405b6107e3d8164b'}\n",
      "\n",
      "\n",
      "{'index': 1, 'timestamp': '02/01/2018', 'data': '{amount:4}', 'previousHash': '1fb6344a6e5c8f0c7e03e1ded0e831a3d92c3741eb5f7153405b6107e3d8164b', 'nonce': 767597, 'hash': '000004c911b7d620a648fd8cec12d2d1cbe838c427f8cb2e12f00eaf64ffe1d3'}\n",
      "\n",
      "\n",
      "{'index': 2, 'timestamp': '03/01/2018', 'data': '{amount:5}', 'previousHash': '000004c911b7d620a648fd8cec12d2d1cbe838c427f8cb2e12f00eaf64ffe1d3', 'nonce': 576083, 'hash': '00000b72782457590c470f83d574438b5bad3d8eb971e9f3e5d2a041107f8db3'}\n",
      "before tamper block,blockchain is valid ###\n",
      "True\n",
      "after tamper block,blockchain is valid ###\n",
      "False\n"
     ]
    }
   ],
   "source": [
    "from hashlib import sha256\n",
    "import time\n",
    "class Block:\n",
    "     \n",
    "    def __init__(self,index,timestamp,data,previousHash=\"\"):\n",
    "        \n",
    "        self.index = index\n",
    "        self.timestamp = timestamp\n",
    "        self.data = data\n",
    "        self.previousHash = previousHash\n",
    "        self.nonce = 0\n",
    "        self.hash = self.calculateHash()\n",
    "        \n",
    "    \n",
    "    def calculateHash(self):\n",
    "        plainData = str(self.index)+str(self.timestamp)+str(self.data)+str(self.nonce)\n",
    "        return sha256(plainData.encode('utf-8')).hexdigest()\n",
    "    \n",
    "    def minerBlock(self,difficulty):\n",
    "        while(self.hash[0:difficulty]!=str(0).zfill(difficulty)):\n",
    "            self.nonce+=1\n",
    "            self.hash = self.calculateHash()\n",
    "    \n",
    "    def __str__(self):\n",
    "        return str(self.__dict__)\n",
    "    \n",
    "    \n",
    "class BlockChain:\n",
    "    \n",
    "    def __init__(self):\n",
    "        self.chain = [self.createGenesisBlock()]\n",
    "        self.difficulty = 5\n",
    "\n",
    "    def createGenesisBlock(self):\n",
    "        return Block(0,\"01/01/2018\",\"genesis block\")\n",
    "    \n",
    "    def getLatestBlock(self):\n",
    "        return self.chain[len(self.chain)-1]\n",
    "    \n",
    "    def addBlock(self,newBlock):\n",
    "        newBlock.previousHash = self.getLatestBlock().hash\n",
    "        newBlock.minerBlock(self.difficulty)\n",
    "        self.chain.append(newBlock)\n",
    "        \n",
    "        \n",
    "    \n",
    "    def __str__(self):\n",
    "        return str(self.__dict__)    \n",
    "    \n",
    "    def chainIsValid(self):\n",
    "        for index in range(1,len(self.chain)):\n",
    "            currentBlock = self.chain[index]\n",
    "            previousBlock = self.chain[index-1]\n",
    "            if (currentBlock.hash != currentBlock.calculateHash()):\n",
    "                return False\n",
    "            if previousBlock.hash != currentBlock.previousHash:\n",
    "                return False\n",
    "        return True\n",
    "            \n",
    "                  \n",
    "myCoin = BlockChain()\n",
    "\n",
    "\n",
    "startMinerFirstBlockTime = time.time()\n",
    "print(\"start to miner first block time :\"+str(startMinerFirstBlockTime))\n",
    "\n",
    "myCoin.addBlock(Block(1,\"02/01/2018\",\"{amount:4}\"))\n",
    "\n",
    "print(\"miner first block time completed\" + \",used \" +str(time.time()-startMinerFirstBlockTime) +\"s\")\n",
    "\n",
    "startMinerSecondBlockTime = time.time()\n",
    "print(\"start to miner first block time :\"+str(startMinerSecondBlockTime))\n",
    "\n",
    "myCoin.addBlock(Block(2,\"03/01/2018\",\"{amount:5}\"))\n",
    "\n",
    "print(\"miner second block time completed\" + \",used \" +str(time.time()-startMinerSecondBlockTime) +\"s\\n\")\n",
    "\n",
    "#print block info\n",
    "print(\"print block info ####:\\n\")\n",
    "for block in myCoin.chain:\n",
    "    print(\"\\n\")\n",
    "    print(block)\n",
    "    \n",
    "#check blockchain is valid\n",
    "print(\"before tamper block,blockchain is valid ###\")\n",
    "print(myCoin.chainIsValid())\n",
    "\n",
    "#tamper the blockinfo\n",
    "myCoin.chain[1].data = \"{amount:1002}\"\n",
    "print(\"after tamper block,blockchain is valid ###\")\n",
    "print(myCoin.chainIsValid())"
   ]
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