Here I’d like to share with you my own thoughts to quickly differentiate Zilliqa from other blockchains as the first line of filters before you raise the comparison questions in our slack channel.
*Scalability does not only mean high throughput but also indicates the large scale of the network.* To compare a blockchain to Zilliqa, you can go through a few questions listed as following.
*1) Is it a permissioned or permissionless blockchain?* As we know, lots of blockchains or new consensus algorithms claim they can process over 100, 000 transactions per second (tps), but they are running in a permissioned setting. This implicates that only registered or privileged nodes are allowed to join their systems, and it does not support open membership. In the real world, lots of banks and big companies are working on this direction to meet their internal requirements, e.g., hyperledger. In contrast, Zilliqa is a public blockchain providing open membership to accept new nodes.
*2) How many nodes do they support?* Another important metric for scalability is the scale of their network. In the permissioned setting, high throughput is relatively easy to achieve, as it only requires a few nodes say a hundred nodes to reach consensus. However, it typically does not scale to a large network, as the underlying consensus protocol does not run effectively when the network size becomes large. The root cause is that different variants of BFT protocols can incur at least O(N^2) communication complexity. For example, assume a message size is 100 bytes, if the network size is 100, at least 1MB (100* 100^2 = 1,000,000 bytes) are transferred, but if network size is 10000, 10,000,000,000 bytes (10 GB) are transmitted to every node, which is unrealistic in the public setting. In contrast, Zilliqa is designed to be scalable. In Zilliqa, we first apply sharding to divide the whole network into relatively small shards say 600 nodes. Then we further employ Schnorr signature and multi-signing schemes to reduce communication complexity from O(N^2) to O(N), which significantly improve the performance of our consensus protocol. Therefore, Zilliqa can survive and scale in the public setting with thousands of nodes in the network.
*3) Does it use PoW or PoS?* PoW is energy-inefficient, but the Nakamoto consensus protocol derived from it can effectively resolve the consensus issue, i.e., choosing the longest chain as the confirmed one with agreement. PoS is energy-efficient and helps the network to elect a consortium of representative nodes. Then these representatives can run consensus protocol like variants of BFT to agree on the same set of valid transactions. Typically the consortium size is small, e.g., 21 in EOS and 100 in Ethereum Casper. We at Zilliqa believe that PoS is still a nascent idea. On the contrary, PoW is a very well understood mechanism which has survived the test of time. Having said that, the use of PoW in Zilliqa is very different from the way it is used in say Bitcoin. This ensures that PoW does not become a bottleneck for scalability in Zilliqa. For the detailed explanation, please refer to Q11 in our FAQ.