LightHash: Photonic Blockchain Based on Optical Proof-of-Work

Stanford inventors have developed a framework that performs digitally verifiable photonic matrix-vector multiplication in integrated photonic networks, which may potentially enable energy-efficient hash functions and cryptocurrency mining. Bitcoin is estimated to consume 113 TWh annually, which is approximately 0.5% of the world's energy. Proposed programmable photonic networks are capable of energy-efficient matrix multiplication operations but are limited by their error, as cryptographic applications require 'consensus' – where several devices agree on a given computation. LightHash decreases systematic error and enables photonic consensus by minimizing bit error rate, such that the matrix operation operates in a limited space of possible outcomes that can be reliably reproduced across many devices. The algorithm is a slight modification of Bitcoin's proof of work, where LightHash achieves at least the same security guarantee.

Figure:

Figure Description:The LightHash protocol for optical proof of work - a) conceptual illustration and b) chip design.

Stage of Development
Prototype demonstrates that a photonic chip can implement a matrix-vector multiplication for a circuit size of 4. The inventors intend to implement LightHash for higher scalability.