lec19

dz / distributed_systems_MIT / lec19

Summary

Lecture 19: Bitcoin

Node Tree

• bitcoin
  • public_ledger
    • peers_transaction_logs_identical
      • easy_to_make_attack
      • majority_vote
        • open_system_controlled_membership_difficult
      • agreement_ledger_despite_malice
    • use_single_trusted_entity
      • doesnt_work_global_scale
  • blockchain
    • two_successors_block
      • fork
        • handling_forks
          • longer_fork_preference
            • manufacture_longer_chain
              • more_CPU_peers
                • non_malicious_network_more_CPU
            • rapidly_chooses_fork
            • chain_grows_prop_num_peers
          • peers_immediately_work_on_successor_block
            • longer_fork_preference
              • manufacture_longer_chain
                • more_CPU_peers
                  • non_malicious_network_more_CPU
              • rapidly_chooses_fork
              • chain_grows_prop_num_peers
    • block
      • hash_prev_transaction
      • signature_prev_owner
      • current_owner_public_key
    • change_blocks_attack
      • cryptographic_hashes_prevent
    • creating
      • mining
        • leading_zeros
          • dynamically_adjust_leading_zeros
            • nonce_hardness
              • peers_agree
                • use_deterministic_function
          • nonce
        • proof_of_work

Nodes

bitcoin
content	Bitcoin
children	public_ledger, blockchain

public_ledger
content	Public Ledger
children	peers_transaction_logs_identical, use_single_trusted_entity (simple idea)
parents	bitcoin

use_single_trusted_entity
content	Simple idea: use single trusted entity
children	doesnt_work_global_scale (why it doesn't work)
parents	public_ledger

doesnt_work_global_scale
content	Doesn't work at global scale
parents	use_single_trusted_entity

peers_transaction_logs_identical
content	Peers: transaction logs should be identical
children	easy_to_make_attack, majority_vote, agreement_ledger_despite_malice
parents	public_ledger

majority_vote
content	Majority vote
children	open_system_controlled_membership_difficult
parents	peers_transaction_logs_identical

easy_to_make_attack
content	Easy to make attack
parents	peers_transaction_logs_identical

open_system_controlled_membership_difficult
content	Hard to build open system with controlled membership
parents	majority_vote

agreement_ledger_despite_malice
content	Agreement on ledger, despite malice
parents	peers_transaction_logs_identical

blockchain
content	Blockchain
children	two_successors_block, block, change_blocks_attack, creating
parents	bitcoin

block
content	Block
children	hash_prev_transaction (item in block entry), signature_prev_owner (item in block entry), current_owner_public_key (item in block entry)
parents	blockchain

hash_prev_transaction
content	Hash of previous transaction
parents	block

signature_prev_owner
content	Signature of previous owners public key
parents	block

current_owner_public_key
content	Current Owner's Public Key
parents	block

creating
content	Creating
children	mining
parents	blockchain

mining
content	Mining
children	leading_zeros, proof_of_work
parents	creating

proof_of_work
content	Proof of work
parents	mining

leading_zeros
content	Leading zeros in hash
children	dynamically_adjust_leading_zeros, nonce
parents	mining

nonce
content	Nonce
parents	leading_zeros

dynamically_adjust_leading_zeros
content	If block creation rate faster than one every 10 minutes, leading zeroes increases. If slower, decrease leading zeros.
children	nonce_hardness
parents	leading_zeros

two_successors_block
content	Two successors to a single block possible
children	fork
parents	blockchain

fork
content	Fork
children	handling_forks
parents	two_successors_block

handling_forks
content	How to handle forks
children	longer_fork_preference, peers_immediately_work_on_successor_block
parents	fork

peers_immediately_work_on_successor_block
content	Peers that see a successor block will immediately start working on it
children	longer_fork_preference
parents	handling_forks

longer_fork_preference
content	Preference for longer fork
children	manufacture_longer_chain, rapidly_chooses_fork, chain_grows_prop_num_peers
parents	peers_immediately_work_on_successor_block, handling_forks

chain_grows_prop_num_peers
content	Rate at which chain can grow is proportional to number of peers
parents	longer_fork_preference

rapidly_chooses_fork
content	Rapidly chooses fork
parents	longer_fork_preference

change_blocks_attack
content	Can you change blocks in an attack?
children	cryptographic_hashes_prevent
parents	blockchain

cryptographic_hashes_prevent
content	Cryptographic hashes prevent this
parents	change_blocks_attack

manufacture_longer_chain
content	Manufacture longer chain
children	more_CPU_peers
parents	longer_fork_preference

more_CPU_peers
content	Possible to do if you have more CPU than all the peers
children	non_malicious_network_more_CPU
parents	manufacture_longer_chain

non_malicious_network_more_CPU
content	non-malicious part of network should have more CPU power
parents	more_CPU_peers

nonce_hardness
content	Hardness of finding nonce
children	peers_agree
parents	dynamically_adjust_leading_zeros

peers_agree
content	Peers need to agree
children	use_deterministic_function
parents	nonce_hardness

use_deterministic_function
content	Use deterministic function on blockchain to find hardness
parents	peers_agree