Source code of blockchain trading computing power system
One of the characteristics of blockchain projects (especially public chains) is open source. Through open source code, to improve the credibility of the project, so that more people can participate. But the open source code also makes it easier for attackers to attack blockchain system. In the past two years, there have been a number of hacker attacks. Recently, the anonymous currency verge (xvg) was attacked again. The attacker locked a vulnerability in the xvg code, which allowed malicious miners to add false timestamps on the block, and then quickly dig out new blocks. In a few hours, the attacker obtained nearly $1.75 million worth of digital currency. Although the subsequent attack was successfully stopped, no one can guarantee whether the attacker will attack again in the future
of course, blockchain developers can also take some measures
one is to use professional code audit services,
the other is to understand the security coding specifications and take preventive measures
the security of cryptographic algorithm
with the development of quantum computer, it will bring a major security threat to the current cryptosystem. Blockchain mainly relies on elliptic curve public key encryption algorithm to generate digital signature for secure transactions. Currently, the most commonly used ECDSA, RSA, DSA, etc. can not withstand quantum attacks in theory, and there will be greater risks. More and more researchers begin to pay attention to cryptographic algorithms that can resist quantum attacks
of course, in addition to changing the algorithm, there is another way to improve the security:
refer to bitcoin's treatment of public key address to rece the potential risk of public key disclosure. As users, especially bitcoin users, the balance after each transaction is stored in a new address to ensure that the public key of the address where bitcoin funds are stored is not leaked
security of consensus mechanism
the current consensus mechanisms include proof of work (POW), proof of stake (POS), delegated proof of stake (dpos), practical Byzantine fault tolerance (pbft), etc
POW faces 51% attack. Because POW depends on computing power, when the attacker has the advantage of computing power, the probability of finding a new block will be greater than that of other nodes. At this time, the attacker has the ability to cancel the existing transaction. It should be noted that even in this case, the attacker can only modify his own transaction, but not the transaction of other users (the attacker does not have the private key of other users)
in POS, attackers can attack successfully only when they hold more than 51% token, which is more difficult than 51% computing power in pow
in pbft, when the malicious nodes are less than 1 / 3 of the total nodes, the system is secure. Generally speaking, any consensus mechanism has its own conditions. As an attacker, we also need to consider that once the attack is successful, the value of the system will return to zero. At this time, the attacker does not get any other valuable return except destruction
for the designers of blockchain projects, they should understand the advantages and disadvantages of each consensus mechanism, so as to select an appropriate consensus mechanism or design a new consensus mechanism according to the needs of the scene
security of smart contract
smart contract has the advantages of low operation cost and low risk of human intervention, but if there are problems in the design of smart contract, it may bring greater losses. In June 2016, the Dao, the most popular funding project of Ethereum, was attacked. The hacker obtained more than 3.5 million Ethereum coins, which later led to the bifurcation of Ethereum into Eth and etc
there are two aspects of the proposed measures:
one is to audit the security of smart contract, and the other is to follow the principle of smart contract security development
the security development principles of smart contract are: to be prepared for possible errors, to ensure that the code can correctly handle the bugs and vulnerabilities; Release smart contracts carefully, do well in function test and security test, and fully consider the boundary; Keep smart contracts simple; Pay attention to the threat intelligence of blockchain and check and update in time; Be clear about the characteristics of blockchain, such as calling external contracts carefully
security of digital wallet
there are three main security risks in digital wallet: first, design defects. At the end of 2014, a user lost hundreds of digital assets e to a serious random number problem (repeated r value). Second, the digital wallet contains malicious code. Third, the loss of assets caused by the loss or damage of computers and mobile phones
there are four main countermeasures:
one is to ensure the randomness of the private key
The second is to check the hash value before installing the software to ensure that the digital wallet software has not been tampered with The third is to use cold wallet The fourth is to back up the private keyFrom the current mainstream blockchain projects, blockchain projects are mainly divided into four categories: the first category: currency; The second is platform; The third category: application category; The fourth type: asset token
currencies mainly act as the "exchange media" in the field of blockchain assets, and the exchange media refer to general equivalents, such as gold and silver bills in the past< (currency exchange on trading blockchain assets)
platform projects refer to the establishment of technical platforms to meet the needs of various blockchain application development, which can rece the threshold of application development on blockchain
application projects cover a wide range of fields, including finance, social networking, games, property rights protection, etc., and are also the fastest growing fields of blockchain assets
asset token project refers to the blockchain mapping of physical assets, that is, the physical assets on the chain. At present, there are no more than 10 varieties
01 currency
the first category is currency project, which is also the earliest blockchain project. Currency projects mainly include bitcoin and lightcoin. In addition, there is another kind of asset with the characteristics of anonymity. Its main functions include protecting the privacy of both sides of payment while realizing payment. The well-known ones are dash, monero and zcash. Currency is mainly used as the "exchange medium" in the field of blockchain assets. The exchange medium is the general equivalent you use to exchange goods. For example, gold, silver and silver bills can be used as the exchange medium in the past. At present, there are more than 2100 types of digital assets in the world, and the number of currency blockchain projects has increased rapidly recently. As of June 2018, bitcoin is still the largest market value
02 platform type
the second type is platform type blockchain project. The main function of platform type blockchain project is to establish a technical platform to meet the technical requirements of various blockchain application development; In short, platform applications allow developers to directly issue digital assets and write smart contracts on the blockchain. Smart contract is a computer program running on the blockchain database, which can be automatically executed under the conditions of its source code setting
for example, you develop a smart contract based on the house rent protocol on the blockchain. When the owner receives the rent, it will trigger the automatic execution and give the security key of the apartment to the tenant
the main function of platform blockchain projects is to establish the underlying technology platform, so that developers can do application development on the underlying technology platform. A considerable number of platforms are still in the development state. As of June 2018, Ethereum has the largest market value
03 application
the third category is application blockchain projects. Application projects are blockchain projects based on blockchain development platform (such as Ethereum), which can solve many problems in various fields of the real economy
for example, augur, Golem, vechain, omisego, which provides asset exchange and transfer services. Using blockchain technology, these projects can better solve the problems of trust and cross-border circulation. At the same time, using smart contracts and tokens on the blockchain, they can better realize automatic execution and greatly improve the efficiency of social and economic activities. Application blockchain projects cover a wide range of fields, including finance, social networking, games, property rights protection and so on. It is also the field with the fastest market value increment of blockchain projects at present
04 asset token
the fourth category is the asset token blockchain project. Asset token refers to linking the blockchain assets to physical assets such as gold and US dollars, which is the blockchain mapping of physical assets. As of February 2018, there are no more than 10 varieties. The typical representatives are usdt against US dollars, digix Dao against gold, Digix each token represents 1 gram of Gold Certified by the London Bullion Market Association. Asset token has the advantages of convenient transaction and safekeeping. First of all, asset token is more convenient for transaction. Because blockchain assets can be split, it has better liquidity
for example, at present, real estate needs to be transferred as a whole. If the real estate can be token, it can be split and purchased, which is more convenient for transaction. Secondly, the token of physical assets is more concive to custody. Gold is easy to wear out and cause losses in physical transactions, but there is no need for physical transfer after the token of physical assets, which is more concive to the custody of physical assets