CS765-Simulate-P2P-CryptoCurrency-Network

• Subject - Introduction to Blockchains, Cryptocurrencies and Smart Contracts (CS 765)
• Semester - Autumn 2021
• Project
  • Build a discrete-event Simulator for a P2P Cryptocurrency Network
    • Assignment 1 - Problem Statement
  • Simulating a selfish mining attack using the P2P Cryptocurrency Network developed in assignment 1
    • Assignment 2 - Problem Statement
• Team Members
  • 203050054 - Fenil Mehta
  • 203059006 - Aditya Pradhan
  • 20305R005 - Arnab Das
• Implementation/Solution
  • Assignment 1
    • Code - src1
    • Report 1
    • Control Flow Chart
    • Design Points
  • Assigment 2
    • Code - src2
    • Report 2 - TO ADD

Points to Note

• Node == Peer == Miner all three mean the same
• txn == transaction
• Unit of time = seconds for everything
• md5 hash function is used for speed - Can be updated to use any other hash function
• GenesisBlock.prev_node_hash = -1
• if a block with block_index < node.curr_block_index_max is received, then it is not dropped because:
  1. The received block can become ancestor of a block which forms a longer chain in future
  2. The block creator would not spend their time and computation power in creating and sending a block which does not create a longest chain
• Transactions created are always assumed to be authentic in this simulation
  • In the real world, they are signed by the transaction creators (i.e. money senders)
• mining reward is always the first transaction of any block, and sender is -1 only
  • Sender == -1 means money is created from thin air
  • If mining reward transaction is placed at any position other than index 0, then it is invalid
  • If id_sender for mining reward transaction is anything other than -1, then it is invalid
• mining_reward_update_percent is used as follows: new_reward = old_reward (1 + mining_reward_update_percent / 100)
  • The above statement will be executed every mining_reward_update_block_time blocks
    • i.e. when longest_chain.index % mining_reward_update_block_time == 0
• Empty blocks are valid
  • Sometimes bitcoin and ethereum have empty blocks
• Any valid transaction created should enter the blockchain even if forks happen
  • We find the common ansestor between the tails of the fork with the help of block index
• Simple Cache is implemented to optimize block validation and creation
• It is assumed that no one will create time pass transactions where sender and receiver are the same
• Clarifications specific to Assignment 2
  • The attacker is a single node
  • In case of more than one attacker nodes, they all will perform attack individually. They do NOT coordinate with each other and are unaware of the existence of other attackers
  • Each attacker assumes that all other people are honest (this assumption is not used by the attacker in any part of the attacking logic)
  • The attacker does not forward blocks generated/mined by other nodes

Execution Steps and Images

Assignment 1

cd src1
python simulator.py --config config.json --debug

Sample Execution Output

Assignment 2

cd src2
python simulator.py --config config.json --debug

References

• Bitcoin and cryptocurrency mining explained
• Proof-of-Stake (vs proof-of-work)
• But how does bitcoin actually work?
• Graphviz Visualization
• Exponential Distribution
  • https://numpy.org/doc/stable/reference/random/generated/numpy.random.exponential.html
  • https://en.wikipedia.org/wiki/Exponential_distribution
• Python specific features
  • Making a python user-defined class sortable, hashable
  • Static Typing in Python
  • https://stackoverflow.com/questions/39740632/python-type-hinting-without-cyclic-imports
  • How does a Python set([]) check if two objects are equal?
• KiloByte (kB) vs. KibiByte (KiB)
  • https://en.wikipedia.org/wiki/Byte#Multiple-byte_units