Compare and contrast between Dfinity, Algorand, Thunderlla, Oasis Lab:
Analysis on Top Tier Blockchain 3.0 Projects
Dfinity：Threshold Signature Scheme – A New Direction for Consensus
This project launched in Silicon Valley in 2016, its founder Dominic is one of the core members of the Early Ethereum Cryptography Association; Dfinity's most prominent contribution to the crypto industry is the introduction of threshold signature technology into consensus algorithms. The consensus idea of Dfinity is as follows: First, the nodes of the whole network are randomly divided into various number of groups (N Groups). At the beginning of each round of consensus, the block nodes and the witness nodes are randomly selected. After the nodes complete the formation of a block, the notary nodes choose which block to be the final block. At the same time, in the process of randomly selecting nodes that forms a block, so that the consensus can be executed continuously. However, since there is no power consumption as a measurement of security prevention – referring to the POW mechanism. Dfinity's block and notary nodes are generated in a group. For example, each block of is formed by 400 nodes. The threshold signature technology is used to guarantees the integrity of the data block, after more than 51% (more than 201 machines) being randomly selected and execute their individual signature, it can then generate data blocks which can be verified by the third party and can generated the random number of next round of nodes to greatly improves the overall security of the network. This system turns an original attack on a single node into an attack of a group of nodes, which becomes much more challenging to successfully execute such attack, thus the overall system security is improved. In the field of cryptography, VRF (verifiable random functions) is a crucial component, threshold signature function is another key component, and the biggest breakthrough of Dfinity is the fact that its technology incorporates both VRF and threshold signature, which guarantees that its algorithm can be implemented. Based on this consensus, Dfinity claims that it has reached hundreds of transaction per second, and the confirmation time for each block is 7.5 seconds.
Dfinity's consensus mechanism is well designed, but there are still flaw remains in the system. Because the establishment process of the "group" in the threshold signature is very complicated, each group needs to be kept for a long time after it’s established. At this time, there is a potential game theory problem, that is, the group signature of the group can be predicted through the collusion of multiple members, and the cost of collusion is very low. Each group members already knows which group they belong, through various means such as the Internet to easily find members of the same group to collude with. Collusion members can collaboratively acquire the group private key through calculation and quickly predict the next round of random numbers, thus undermining the integrity of the network. Because such attack is very difficult to find, and attack can be achieved with no cost. We have already submitted this question to the Dfinity team and have not yet received a response.
Algorand：Consensus Based on Random Calculation with Impressive TPS
Algorand is the Blockchain Consensus Agreement released by the Turing Award winner and Professor Sivio Micali from MIT in May 2017. The main idea here is to combine the random selection and BFT algorithms to achieve high TPS on a completely decentralized network.
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The first step, the role confirmation phase: For a large-scale network, each node starts with a VRF (verifiable random functions) to generate a voucher, the node randomly selected with such voucher and participating in the consensus is called "the voter", and the one with the smallest voucher value is selected as the "proposer".
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The second step, the consensus grading phase: the proposer is responsible for assembling the candidate blocks, and then the voters agree upon the leader node of the current round, and they are also responsible for confirming the potential blocks
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The binary Byzantine phase: the verified votes will vote for candidate block, that is, either accepts the candidate block (there is no problem in the block) or does not accept the candidate block (the block is considered to have an error, such as double spending, and do not accept the block, while replace it with an empty block)
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The final step would be to broadcast data to the entire network: Algorand effectively improves the system's TPS on the basis of ensuring network security by randomly selecting the consensus nodes every round. According to the data given in the paper, the consensus transaction is 750 Mbytes per hour, according to Bitcoin, each transaction length starts from 250 bytes. Thus the calculation would be 75010241024/60/60/250=873.8 TPS;
As we introduced and summarized the details of Algorand algorithm above, let’s now discuss how there is still some room for improvement.
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Algorand's main function now is to transfer transactions, its function is similar to that of Bitcoin, and as the most important smart contract improvement in Blockchain 2.0, Algorand did not discuss how to support smart contracts the Algorand's network.
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Algorand network operate under the assumption that the amount of “honest” voter notes are over 2/3, but did not mention how they would guarantee the honesty of the net work.
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Algorand's algorithm requires completely random selection at each step of processing. Frankly speaking, the overall complexity of the project remain high. After the paper was published, Algorand has organized the team to quickly promote the development of the project, and the community has being waiting for Algorand's engineering establishment
Thunderlla：Combining the POW and the POS
The founder of Thunderlla is Elaine Shi, a professor of computer science at Cornell University. Thunderlla proposes a new algorithm, assuming the accelerator node and over 3/4 of the committee node in the network are “honest” nodes, while the network is functioning well, Thunderella can implement fast asynchronous processing with a confirmation time within <1 second, and can process all transactions almost instantly. And when there is an abnormality in the network, such as the emergence of the Byzantine failure, the network will start the cool-down mechanism and switch to the traditional Blockchain consensus (with slower processing performance), to ensure the security and sustainability of network, while restoring the system. Once restoring is completed, it automatically switch back to the original mode. As a result, most of the time during optimal situation, the network exceeds the processing speed of the current Blockchain by over 1000 times, and when potential issues emerges, the malicious node can still resist 49% attack through the traditional (slow) chain approach. For traditional chain approach, Thunderlla can operate on Bitcoin, or on Ethereum, or any other blockchains, that is, instant creates a friendly, safe and reliable atmosphere in a malicious environment.
This algorithm can be seen as a mixture of POS and POW, hoping to have the advantages of both POW and POS algorithms, but there are several key issues here that remains questionable, such as how does Thunderlla ensure that 3/4 committee member nodes are honest and how to remove the malicious committee members is not explicitly mentioned; and the restart mode is still not clear defined, for example how do we select the next accelerator。In terms of progress, Thunderlla has yet to announce any further progress after the publication of the paper.
Ekiden of the Oasis Lab：Performance Improvement Based on a Trusted Environment
The project was launched in 2018 and its founder, Dawn Song, is an associate professor of computer science at the University of California at Berkeley. Ekiden's main idea is to separate the consensus layer from the computing layer; in the computing layer, the hardware is composed of TEE (Trusted Execution Environment, such as Intel's SGX), and the calculation of the smart contract is execute through Tee, and the consensus layer Use POW or POS to verify the result of TEE calculations. This method has two characteristics: 1) the calculation node and the consensus node are separated, and the computational node can execute with arbitrarily complex logic, the calculation result is mutually verified by a small number of trusted computing nodes, so the execution efficiency is high, basically as efficient as executing on a single machine. The network also support execution of multiple contracts simultaneously with different machines; 2) Privacy protection, only the encrypted data (even the encrypted contract code) is stored on the chain, the decryption is only done in the TEE, and then the result is calculated and returned to the chain with encryptions.
From the overall design of Ekiden, its security relies entirely on the TEE's trusted execution environment. Although it solves the security problem ingeniously, there are security risks remaining. On March 2017, Graz University of Technology in Austria, researchers have cracked the protection of SGX. Therefore, it is still time to check whether the security of a single hardware is reliable. At the same time, the principle of TEE is that the private key is stored at the chip manufacturer. For example, SGX is the private key that is responsible for Intel, so the chip The producer has become a centralized node and has did not fulfill the concept of complete decentralization of the blockchain.
In terms of progress, Ekiden's is quite impressive. The website has already allowed users to submit their own machine configuration to test the network application, but there is no data on the performance of the test network.
