CSCI301-Assignment 3 Solved

Q1. Create a simple blockchain system for playing a tic-tac-toe game between two parties, Alice and Bob.  

 

Both players have an initial block to start their play. Let Alice always start first for simplicity. The initial block, Block0.json, for both Alice and Bob is set as follow:  

{

"TxID": 0,

"Hash": "This is the genesis block.",

"Nonce": 0,

"Transaction": []

}
Figure 1. Block0.json 

At each turn, a player (e.g., Alice) who takes the turn creates a new block in JSON format and send it to the other player (e.g., Bob) who plays tic-tac-toe together. Each block is formed as follows:

{

“TxID": <TxID,

"Hash": "<Hash ", "Nonce": <Nonce,

"Transaction": <Transaction

}

The entities in the above block are computed in a way described as follows:

1. <TxID is an incremental counter, which increased by 1 on each turn.  

 

<TxID of a new block = <TxID of the last block + 1
 

2. “Hash” is the output of the SHA256 hash with the last block and “Nonce”. The player increases the value of “Nonce” from 0 by 1 until the value of the hash output is less than 2248.  

 

<Hash = SHA256(<The last block||<Nonce) < 2248
 

HINT: You may need to convert <The last block and <Nonce to a set of bytes so that they can be taken as inputs of SHA256. You can convert them using String encode() method. After the conversion, you can append <Nonce to <The last block. (e.g., str(i).encode() where i is <Nonce and set as integer.)  

 

3. “Transaction” is the choice of the player in its turn. It contains the player name and its choice of the space on the tic-tac-toe board (e.g., [“Alice”,5]). To make your code simple, assume that Alice and Bob take a random empty space in their turn.

 

 

For example, Assume that we use the following grid to play a tic-tac-toe game.

1 
2 
3 
4 
5 
6 
7 
8 
9 
 

The first block (block1.json) is generated by Alice as follows.  

               {

                              “TxID”: 1,

                              “Hash”: "00e260d79735cd52f38358289f890019e376117be1866

    027e172c391383ff5b8”,

                              “Nonce”: 11,

                              “Transaction”: [“Alice”,5]

               }

Note that in your program, Alice must choose a space, randomly. Then, Alice saves the block in her storage and sends it to Bob.  

 

Once Bob receives the block, Bob validates the received block and save it to its storage. Then, Bob creates a following block and send it to Alice:  

               {

                              “TxID”: 2,

                              “Hash”:“0053560513cc0535db6692c972aab41ec30ec9ec3b43a5

   b0b0f1c8eafce20c3f”,

                              “Nonce”: 742,

                              “Transaction”: [“Bob”,1]

 }

Note that in your program, Bob must randomly choose a space among the spaces not taken previously.

 

The game will continue until all spaces on the board are taken. Alice and Bob keep each block in a separate file (block0.json, block1.json, …, block9.json) in