What is a 51% attack?
A "51% Attack" occurs when the attacking side, that can be represented by a comparatively small number of miners, has a "controlling stake" of the total hash rate, that is, computing capacity. As a result of the attack, the miners gain control over the entire network and can create blocks at their discretion.
If the miner or the pool of miners controls more than half of the hash rate, then they have the ability to fully control the network: they can add new blocks, manipulate two-way operations and not confirm new transactions.
How is work with nodes on the Credits platform organized? And how are the transaction nodes assigned (consensus)?
On the Credits platform, the node assignment is based on the DPoS (Delegated proof-of-stake) algorithm, which is an algorithm for achieving consensus in a decentralized environment. The main principle of DPoS operation is the division of voting and validating participants.
The node assignment operation occurs within a single round. The frequency of rounds is five rounds per second. Asynchronous rounds are supported, the new one starts to be executed before the completion of the previous one.
The nodes that provided the hash within the specified time are included in the list of nodes receiving the right to participate in the consensus procedure. The node that was the first to send the hash of the last block becomes the main node (it is selected at random), the remaining nodes (within the required number) are considered trusted or common. Trusted nodes exchange among themselves using the BFT algorithm, which allows them to monitor the network state and exchange messages, thereby ensuring honest decision-making about the operation of transactions and the pool. From the list of trusted sites (selected randomly), the writing node is selected. It writes the generated block to trusted nodes, forms a hash of the block (the hash of the previous block + its own) and sends it to be written to all nodes of the network.
How much resources are needed to organize the 51% attack (expediency and payback).
The system uses a trust coefficient that is an absolute fractional numerical value from 0 to 1, expressed in mathematical terms of the number of trusted nodes + 1 to the total number of nodes in the network. The maximum number of trusted nodes can not exceed 50% of total network nodes.
Bypassing the consensus algorithm is the only possible way of hacking the system. Injecting transactions with false calls or transaction pools into the system requires a large number of spoof nodes. The huge amount of resources needed to rent large data centers, develop malicious code, deploy password nodes makes attempts at hacking economically unjustified.
The use of modern technologies in the field of data encryption and hash fields has made it possible to develop a platform that can not be hacked unless significant resources and costs outweigh the potential profit.
Using the DPoS algorithm, selecting the main node, trusted nodes, the writing node randomly makes the attack 51 imposible.