Is the health code an "agreement" or a "consensus"?

In fact, the problem that the health code needs to solve is very simple, that is, to reduce the flow of high-risk groups. But for this kind of judgment generated by algorithms such as "spatial dimension" and "temporal dimension", can it continue to bring value after the epidemic ends? Let's review the Bitcoin network system with a complete consensus system and secure network operation and maintenance.

The background of the emergence of Bitcoin originated from a financial crisis. It is based on the blockchain technology of the consensus mechanism and adopts PoW (Proof of Work). It obtains rewards by competing for the right to keep accounts, realizing a transparent, tamper-proof and distributed transparent ledger-based operation mode. In more than ten years of operation, decentralized Bitcoin has been recognized by more and more people.

The concept of proof of work was initially formed in 1993. Its main function was to prevent server attacks and other abuses of services. It was not until 2009 that Bitcoin used it as a consensus mechanism, mainly used to verify transactions in each block of the blockchain. In simple terms, it works by miners competing with each other to see who can solve the complex computing puzzle first. Once a miner calculates the answer to a block, the entire block network will be broadcasted. The remaining miners will verify whether the answer is correct to confirm the block, and reference the hash value of the block to form a new block on the chain ending with the block.

Protocols, for blockchain, are the various rules that constrain it, and the consensus algorithm behind it is the principle by which these rules are implemented. In addition to the financial system, blockchain technology is also used in various business fields, and the "health code" is, to a large extent, just an agreed rule and a protocol.

Consensus is the key to maintaining the integrity and security of the digital currency network. Simply put, it is to allow distributed nodes to reach a consensus and push them towards the longest chain recognized by the nodes. Of course, there will be forks to form new chains, which will in turn generate new protocols and consensus.

Taking Bitcoin as an example, the consensus algorithm is not only a key factor in maintaining the integrity and security of the Bitcoin network, but also makes Bitcoin highly resistant to attacks, such as the "51% attack", which is to control 51% of the computing power to rewrite the on-chain data.

At its peak in 2013-2014, Ghash.io’s computing power accounted for nearly 51%, which not only caused a strong reaction in the community, but also, as a mining pool, Ghash.io also dispersed computing power to maintain the normal operation of the entire chain. Similarly, when approaching this situation, miners and the entire market will also trigger corresponding actions to prevent such a situation from happening. Behind each computing power number is not only an expensive mining machine, but also the long-term interests of a large number of miners themselves.

The relationship between computing power and security may be similar to a logarithmic relationship, similar to, computing power drops by 10%, security drops by 1%; computing power drops by 9 times 10%, security drops by (1-0.99^9)*100%=8.65%. In January 2018, the total network computing power was less than one-sixth of what it is now, but almost no one thought that the Bitcoin network was less secure than it is now.

Although the fluctuation of the coin price will force some mining machines to shut down, what it presents to the Bitcoin network is more of a difficulty adjustment, that is, the average block time of the current difficulty cycle is extended from 10 minutes to more than ten minutes; more advanced mining machines replace the main market players. These will not pose a threat to the security of the Bitcoin network.

Taking BCH as an example, on the evening of April 8, 2020, BCH completed the halving from 12.5 block rewards to 6.25 block rewards. After the first block was mined after the halving, BCH did not produce a block for nearly 2 hours. This is because with the completion of the halving, the block reward decreased and the unit mining income fell accordingly. Some mining machines chose to switch to other SHA256 algorithm currencies or temporarily shut down, while the difficulty remained the same, resulting in a slow block speed in a short period of time. However, BCH uses DAA to adjust the difficulty block by block, so it quickly adjusted the difficulty in subsequent blocks to restore the block time to normal levels.

Just like the Bitcoin network, in the ever-changing social context, although we all have parts that we cannot choose, what we need to do is to constantly think about technology and systems so that they can better safeguard the rights and bottom lines of society and individuals.