Towards Optical Proof of Work

The current cryptocurrency Proof of Work (PoW) ecosystem relies heavily on energy cost to ensure some semblance of decentralization and, in turn, safety. However, the growing energy consumption of cryptocurrency mining has some undesirable effects. This paper proposes a novel approach to alleviate this reliance on energy cost by designing a PoW algorithm, oPoW, that is tailored to ultra-energy-efficient photonic co-processors. While the security of the system still relies on the mining process being costly, the cost in oPOW is concentrated in capital expenses (CAPEX). The oPoW scheme involves minimal modifications to Hashcash-like PoW schemes and thus inherits many properties from such schemes, including basic safety/security from the SHA hash function. The new, additional properties follow from an assumption that photonic co-processors can compute certain functions with greater energy efficiency and speed than traditional digital ASICs. We provide a general theoretical framework for such schemes in addition to suggesting a particular instantiation of this framework to realize oPoW. We provide empirical evidence to support this assertion, as well as a description of a prototype hardware implementation and its working princi-