  The sharing economy is centralizing services, leading to misuses of the
Internet. We can list growing damages of data hacks, global outages and even
the use of data to manipulate their owners. Unfortunately, there is no
decentralized web where users can interact peer-to-peer in a secure way.
Blockchains incentivize participants to individually validate every transaction
and impose their block to the network. As a result, the validation of smart
contract requests is computationally intensive while the agreement on a unique
state does not make full use of the network. In this paper, we propose
Collachain, a new byzantine fault tolerant blockchain compatible with the
largest ecosystem of DApps that leverages collaboration. First, the
pariticipants executing smart contracts collaborate to validate the
transactions, hence halving the number of validations required by modern
blockchains (e.g., Ethereum, Libra). Second, the participants in the consensus
collaborate to combine their block proposal into a superblock, hence improving
throughput as the system grows to hundreds of nodes. In addition, Collachain
offers the possibility to its users to interact securely with each other
without downloading the blockchain, hence allowing interactions via mobile
devices. Collachain is effective at outperforming the Concord and Quorum
blockchains and its throughput peaks at 4500 TPS under a Twitter DApp
(Decentralized Application) workload. Finally, we demonstrate Collachain's
scalability by deploying it on 200 nodes located in 10 countries over 5
continents.
