First. Developer centralization, or community centralization.
There is no doubt that for public blockchain projects, decentralization is a very important feature of it. However, the development technology of this public chain is not mastered by everyone, so in fact, its development ability is still in the hands of a small number of core developers. This creates developer centricity.
On the other hand, blockchain, as a decentralized distributed system, may not have a center. But to form such a community, there may be a center running. The maintainers of this community may guide everyone for their own benefit, which ultimately leads to community centralization. In the past, the TheDAO incident on Ethereum led to a split in the Ethereum community, resulting in two different cryptocurrencies, ETC and ETH. This is all due to community centralization.
Second, the mining pool computing power is concentrated.
Mining is like a lottery. The probability of winning is determined by the hash power of the miner. Small miners do not have enough computing power to stabilize the success of the lottery, that is, to mine. For example, there may only be one day in a month where a block is mined to receive a reward, and the income from that day can subsidize an entire month's expenses. But this also makes the income very unstable, in order to make the miners more stable income, miners to form a mining pool, to cope with the growing computing power. Although mining pools bring stable income to miners, they also bring new problems. Mining pools centralize this scattered computing power and manage it uniformly, as the scale of control continues to expand. When the total computing power reaches or exceeds 51% of the entire network. Even in terms of probability, maybe thirty percent is enough. In this case, the mining pool can control the accounting rights of the blockchain, and it is possible to attack and modify the ledger, and prevent others from mining, thereby threatening the security of the entire system.
Third, cryptographic algorithms may have hidden dangers.
We all know blockchain technology, and the basis for making it trustworthy is its cryptography principle. Cryptographic algorithms designed today are mainly provably secure and computationally secure, not absolutely secure. With the advancement of cryptanalysis technology and the gradual improvement of human computing power, many cryptographic algorithms will expose weaknesses.
Some cryptographic algorithms that were widely used in the past and were considered secure at the time, such as MD5, SHA1. By now, they have been declared cracked or no longer secure. Therefore, it is only a matter of time before these cryptographic algorithms are broken.
On the other hand. Perhaps cryptographic algorithms themselves can prove fine, but the implementation of the algorithm, that is, the implementation of the program, may have vulnerabilities or backdoors. For an immutable system like blockchain, it could be fatal.
Fourth. There is no real anonymity. This makes privacy unguaranteed.
Every transaction in Bitcoin is publicly available on the blockchain ledger, and through various data mining techniques to analyze/transactions that have occurred at each address, relationships between many accounts can be discovered. There are studies that have shown. With privacy measures in place, 40% of Bitcoin user identities can still be identified.
On the bright side, we can think that government regulators can detect crimes such as money laundering and bribery, but from the technology itself, this does not guarantee the privacy of users. Leak your real identity and expose all of your transactions, even those that have occurred in the past.
Therefore, when using blockchain technology in various industries, what kind of privacy protection strategy to adopt will also be the main research content.
Fifth. Security of the wallet.
An important basis for owning Bitcoin and using Bitcoin is the private key. Usually, these private keys will be stored in the wallet, so the security of the wallet is very important. With the current blockchain design, once the private key is lost, the user will no longer be able to use the corresponding bitcoin. At present, the types of wallets are roughly divided into, online wallets. Offline cold wallet. Hardware storage. Key shared storage. Paper media. And brain memory, and so on. In fact, except for the first online wallet, most of the other wallets are relatively safe, but in fact, the vast majority of users now use online wallets. It is equivalent to escrow the key to a trusted authority, which in itself goes against the decentralized idea of the blockchain. However, other than online wallets, users usually need to keep their own safekeeping. Once lost, it cannot be retrieved. Therefore, although the wallet is easy to use, the security needs to be guaranteed by others. Various other ways of self-storage, although safe, are very inconvenient to use, so according to the needs of blockchain applications and assets, a safe and convenient wallet protection mechanism is particularly important.
Sixth, new problems brought about by new technologies and applications.
The earliest blockchain project, Bitcoin, used PoW Proof-of-Work. This mechanism is extremely wasteful of electricity. As a result, people proposed the POS proof-of-stake mechanism. But it brings new problems, such as "disinterested" attacks in the event of forks. There are also other consensus algorithms, such as DPOS-authorized proof-of-stake mechanism, PBFT practical Byzantine fault-tolerant algorithm mechanism. They each have their own advantages and limitations, and we need to choose different types of consensus algorithms according to the business development of different industries to achieve a balance between security, efficiency, and performance.
Summary
So much of the above is the problem of blockchain technology. But don't lose faith in blockchain, these are all due to the immaturity of blockchain in the early days. As technology continues to evolve, blockchain technology will become more mature, and these problems will be solved one by one, or limited to a certain acceptable range.