Quorum

Quorum is a distributed ledger technology implementation that was customized and extended from Ethereum code base, and provided alternate transaction management and contract privacy fitting the needs of financial industry. More specifically, it forked out of an early version of Geth client implementation.

To address transaction and contract privacy issues with the public version of Ethereum blockchain, Quorum introduced the public and private state, where the public state would be shared and accessed by all nodes, and private state only accessed by nodes with permissions. In a similar way, it puts the read-only restriction on the private contract when it accesses the public state, to prevent the private data been propagated to the public state. You can think Quorum manages to have both public blockchain and private blockchain on the same blockchain. In doing so, it has to customize Geth to manage the global state root and state Pritrica tire, to accommodate the separated public and private state, as well as the transaction/block generation logic impacts because of dual states.

A node can differentiate public transactions (unencrypted payloads) vs private transactions (encrypted payloads). It will ask a transaction manager to decrypt the private transactions, which in turn determines if the node has the permissions to decrypt the message. If it has the permissions then transaction manager will decrypt the transaction payload, and allow the node to process the transaction.

As shown in the picture below, encryption and decryption of transaction payload is delegated to the crypto enclave, which also holds all private keys for all involving parties.

Another key area for customization is to implement Istanbul BFT consensus algorithms instead of using Ethereum Estash based PoW algorithm, where nodes with permissions are invited to a simple voting mechanism through a smart contract. Together with the design of offloading cryptographic computations to the off-chain enclave, it greatly improved transaction performance and increased scalability.

Quorum is widely adopted across the industries. We list out some of the usages of Quorum in the following table:

Industry	Quorum usages
Supply Chain	Starbucks & LVMH (luxury goods company)
Financial Services	IIN
In Oil and Gas	VAKT
Trade Finance	Komgo
Digital	Accenture

This article is written in collaboration with Brian Wu who is a leading author of “Learn Ethereum: Build your own decentralized applications with Ethereum and smart contracts” book. He has written 7 books on blockchain development.

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