"Blockchain Principles and Technology" Study Notes Part Six
4. Blockchain network layer
1. Network layer security
Common attacks against the blockchain network layer include:
1.1 Distributed denial of service attack (DDos)
By actively sending a large amount of false information to network nodes, the subsequent access to these information points to the victim to achieve the attack effect.
1.2 Extensive Attacks
Network scalability attack: The attacker maliciously pays high fees to increase the verification priority through external false transactions, thereby blocking the transaction queue and wasting time and bandwidth resources for honest nodes to compete with the attacker.
Transaction malleability attack: The attacker listens to asynchronous unconfirmed transactions, changes the original transaction ID by modifying the transaction signature, and generates a new transaction for broadcast and confirmation. The original ID cannot be confirmed.
Solution: Segregated witness (Segwit)
removes the signature from the transaction and generates a hash value of the block header, so that the signature change does not affect the transaction hash.
1.3 Eclipse attack
By occupying the routing table of the node, the attacker controls the external communication of the node and keeps it in an isolated network. In this way, attacks such as routing spoofing, denial of service, and ID hijacking are carried out.
1.4 Segmentation attack
The attacker assigns honest nodes to different subtrees to contribute computing power and breaks them separately.
1.5 Delay attack
Intercept requests from honest nodes and return outdated blocks.
5. Blockchain Security and Attacks
1. Why is the blockchain insecure?
1.1 Blockchain Hierarchical Architecture Perspective
1.2 Six types of hidden dangers of blockchain
Common six types of safety hazards :
| Cryptography | Blockchain Trust Foundation | Hash algorithm, digital signature, random number |
| user private key | User Participation Credentials | Defense Against Rainbow Attacks |
| Node system security | traditional security | Buffer overflow, distributed node reliability, API interface, etc. |
| Underlying Consensus Protocol | blockchain consistency | Difficult-to-prove protocol security, impossible triangular relationship |
| smart contract | Blockchain business logic | Contract loopholes, contract credibility, and standardization of contracts |
| Incentives | Good Blockchain Ecology | Prevent Ponzi Schemes |
Examples of safety hazards
-
Data layer: Rainbow attack
Rainbow table: A table prepared for the encrypted hash func inverse operation, composed of a combination of public key and private key.
Then let the public key on the rainbow table and the public key on the blockchain collide and pair
. If the public key is successfully paired, the private key will also be exposed to hackers. -
Ponzi schemes
use the money of new investors to pay interest and short-term returns to old investors to create the illusion of making money and defraud more investment.
1.3 Network Connectivity and Blockchain Security
- The lower the connectivity of the network, the more likely the system will be bifurcated, and the less computing power miners will need to carry out a 51% attack
- The greater the difference in network connectivity, the lower the computing power required for a miner with better connectivity to launch a 51% attack.
2 How to make the blockchain insecure
- Attacks on basic components and facilities:
Hash collisions, security threats to P2P networks - Attack the core design of the system: security threats at the consensus layer, security threats at the contract layer, and security threats at the data layer
- Attacks on application ecology: attacks on trading websites, attacks on digital currency/wallet apps
- Attacking the blockchain: security of private keys during operation and storage (asset security after loss), code reliability and protocol security of smart contracts, privacy and security of transactions
3 How to make blockchain more secure
- Human-subjective enhancement:
Holders increase security awareness, developers develop cautiously, and entrepreneurs pay attention to risks - Blockchain system vulnerability optimization
- Combining with other technologies to improve blockchain security