Rollups : a Powerful Scaling Mechanism

One of the major challenges in the world of blockchains is that of scaling up, particularly in terms of throughput, i.e. the number of transactions per second. One way to increase throughput is to use a block validation system other than the one based on proof of work, for example with a classic consensus algorithm between a small number of participants. This would result in a profound change in governance and ultimately a different appreciation of security. Moreover, it is not applicable for an already existing blockchain. Other solutions would be to increase the block size or the block frequency, but these are not viable long-term solutions.

Another idea, relevant in the case of an already established blockchain, is to process a number of off-chain transactions. Synthesis mechanisms allow to confirm on the main chain transactions performed outside the chain.

In this context, the mechanism that is predominantly considered is that of rollups, which we explore in this perspective paper, with the two variants optimistic rollup and ZK-rollup. Three companies, ConsenSys, Protocol Labs and Cometh present the industrial interest they see in these technologies, respectively represented by Nicolas Liochon, Anca Nitulescu and Jérôme de Tychey. In addition, Sarah Bordage and Youssef El Housni, two doctoral students from the École Polytechnique computer science laboratory, specialists in zero-knowledge cryptographic protocols, will provide some insight into the underlying cryptographic mechanisms.