Blockchain smart contract vulnerability
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 keythree characteristics of smart contract in blockchain can be summed up:
1) decentralization. It doesn't rely on the centralized server and runs automatically through the network nodes
2) good trust mechanism. The crisis of trust is greatly reced, and it is not necessary to consider whether the participation is trustworthy
3) high degree of autonomy. Once the condition is triggered, the contract will be executed automatically without interference
the data of smart contract can not be deleted or modified, but can only be added. The history of smart contract can be traced, and the cost of tampering with the contract or breach of contract will be very high, because its evil behavior will be forever recorded and widely known.
Recently, Vulcan team of 360 company found a series of high-risk security vulnerabilities in EOS, a blockchain platform. It is verified that some of the vulnerabilities can remotely execute arbitrary code on EOS nodes, that is, they can directly control and take over all nodes running on EOS through remote attacks
In the early morning of May 29, 360 reported this kind of vulnerability to EOS official for the first time, and assisted it to repair the security risks. The person in charge of the EOS network said that the EOS network will not be officially launched until these problems are fixed 
EOS super node attack: the virtual currency transaction is completely controlled
in the attack, the attacker will construct and publish a smart contract containing malicious code, and the EOS super node will execute the malicious contract and trigger the security vulnerability. The attacker then uses the super node to pack the malicious contract into a new block, resulting in the remote control of all nodes in the network (alternative super node, exchange recharge withdrawal node, digital currency wallet server node, etc.)
because the system of the node has been completely controlled, the attacker can "do whatever he wants", such as stealing the key of the EOS super node and controlling the virtual currency transaction of the EOS network; Obtain other financial and privacy data in the participating node system of EOS network, such as digital currency in the exchange, user key stored in the wallet, key user information and privacy data, etc
What's more, an attacker can turn a node in the EOS network into a member of a botnet, launch a network attack, or become a free "miner" to extract other digital currency
source: Science and Technology News
security audit of smart contract is common in the blockchain instry. There are many loopholes in the public chain projects of blockchain, so the security audit of smart contract is still in great demand. Time security has just launched security audit business. It's not clear what it does. They have been engaged in blockchain for so many years, so they should still have some strength
which friend used the era security wallet? What advantages do they have compared with Youn wallet
the purses suppliers of the two enterprises are good. Fortunately, I know something about them. Let me make a comparison:
1. Behind the security of the times is bitage group. Bitage everyone should know that Huang Tianwei started trading for 13 years, and now it has been 8 years. His popularity and reputation are very reliable, and trading can't do without purses, Although era security was introced in the early 20th century, it can be seen that they are very professional in the field of wallet. Therefore, from these two points of view, there is no need to worry about security at all; It's said that Youn wallet was started in 15 years. Behind it, Taiyi technology is also a powerful company. In recent two years, it has started to develop enterprise wallet, which is also very professional. So in terms of security, there is no need to worry about it
2. Let's compare the procts. Time security is an enterprise wallet proct launched at the beginning of the 20th century, and it's only one year now, while Youn launched it in the 19th, and Youn also launched a hardware wallet. In terms of proct ecological perfection, time security is slightly inferior, mainly because there is no hardware wallet
3. In terms of service fee, the monthly fee of Enterprise Cloud wallet of time security is 500usdt, while the monthly fee of Youn wallet is about 12000 RMB, so in this respect, time security has obvious advantage in price. The reason why the price of time security is so cheap may be that it is only now that we have started to fight the market
the above is my understanding of the wallet suppliers of these two enterprises, which may be biased. Please correct me.
1-security problem: one of the key problems is security and trust. The smart contract system is designed to be an environment without trust, which means that the mistakes can not be corrected
2 - Privacy: one of the challenges of effective use of blockchain is to provide thorough transparency
3 - unexpected scenario problem: smart contract sounds very good, but how to correctly and appropriately handle the contract execution in unexpected scenarios is a problem.
On June 8, 360 exposed the high-risk vulnerability of EOS, which caused a lot of hot discussion among networks. In the early morning of June 2, Beijing time, EOS officially acknowledged to the 360 security team and offered a reward of US $30000, strongly calling on the security community to work together to ensure the continuous improvement of EOS software security
360 exposed EOS vulnerability, if exploited, can control every node and every server in the EOS network, not only take over the virtual currency, various transactions and applications in the network, but also take over all participating servers in the node. It can be said that if someone makes a malicious smart contract, all the digital currencies in it can be taken away directly
the attack of EOS vulnerability can spread among multiple nodes and super nodes at the speed of seconds. The continuous propagation from the control node to the generation of new blocks is a continuous and chain explosion action. It is likely to take over all nodes and complete the operation in 20 seconds
imagine that when the attacker has obtained the supreme authority in the entire EOS network, it is equivalent to mieba putting together all six cosmic protoliths, and can change rapidly in the universe and do whatever he likes
source: China News
the smart contract based on blockchain technology can not only give play to the advantages of smart contract in cost efficiency, but also avoid the interference of malicious behavior on the normal execution of the contract. The smart contract is written into the blockchain in digital form, and the characteristics of blockchain technology ensure that the whole process of storage, reading and execution is transparent, traceable and tamperable. At the same time, a set of state machine system is constructed by the consensus algorithm of the blockchain, so that the intelligent contract can run efficiently.