Better than best: Most efficient quantum-safe and privacy-preserving blockchain protocol gets an upgrade

15 September 2021

Experts Dr Muhammed Esgin, Dr Ron Steinfeld and Raymond Zhao from the Department of Software Systems and Cybersecurity at Monash Faculty of Information Technology have designed and implemented MatRiCT+ – a significantly improved version of ‘the world’s most efficient blockchain protocol’.

Patented by CSIRO’s Data61, the data and digital arm of Australia’s national science agency, and licensed to cryptocurrency provider Hcash, MatRiCT was celebrated for its high level of security against quantum computers and protection of its users and their transactions. This enhancement, also patented by CSIRO’s Data61 and now Monash University, ensures a more practical, quantum-safe and privacy-preserving blockchain protocol.

MatRiCT+ significantly reduces communication and storage costs of transaction messages by up to 25 times. It also accelerates the transaction generation and verification running times to reduce latency and energy consumption by up to 11 times.

Led by Dr Esgin, who’s also affiliated with CSIRO’s Data61, these improvements were achieved through several novel and efficient techniques that could be applied in future designs of protocols that safeguard privacy.

‘The main practicality improvements in MatRiCT+ compared to MatRiCT arise from the new techniques we developed to better exploit the mathematical structures underlying our quantum-safe cryptographic algorithms.’ Dr Esgin said.

‘In particular, some allow us to encode, or “pack”, hidden transaction amounts using significantly fewer bits than required by MatRiCT – while still proving the correctness of the transaction.’

Other techniques enhanced the transaction verification process and its security analysis, enabling the reduction of transaction sizes while obtaining the same level of security against double spending and payment authenticity attacks.

‘Another novel technique allows us to 'compress' the length of transactions that may have many paying accounts, to be not much longer than transactions involving a small number of accounts.’ Dr Steinfeld further explained.

MatRiCT+ follows the Ring Confidential Transactions approach used in Monero, the largest privacy-preserving cryptocurrency. Unlike Bitcoin and Ethererum, Monero transactions don’t reveal sensitive information such as addresses and amounts. What’s more, cryptography algorithms used in popular blockchain-based applications such as Bitcoin are vulnerable to quantum computing attacks.

‘To demonstrate the protocol’s computational practicality, we also developed optimised software for its cryptographic algorithms using state-of-the-art implementation techniques,’ Mr Zhao said.

‘Beyond proof systems, our techniques can be valuable in other real-world applications such as e-voting, e-cash systems and anonymous credentials.’

The new protocol, reported in the researchers’ pre-print paper, has been accepted for presentation at the prestigious IEEE Security & Privacy 2022 conference.