Blockchain Scheme Based on Evolutionary Proof of Work

In recent years, applications of the Blockchain concept, esp. as ledger for bitcoin transactions, has already resulted in huge amounts of wasted electrical energy for performing the Proof-of-Work tasks (cryptographic puzzles). Here, we consider an alternative concept to have this energy used at least for a useful purpose, the solution of real-world optimization problems. By means of the Traveling Salesperson Problem as model problem, we propose a concept to use optimization algorithms in an iterative manner to provide the Proof-of-Work needed to expand the Blockchain by a new block. The basic idea is to improve the tour cost for the best tour found for block n, extended by adding one more city, as a requirement for the inclusion of a new block in the Blockchain. This allows for the design of limited Blockchains, solving the underlying combinatorial optimization problems at the same time. Independently, it calls in for new efficient optimization algorithms and can serve as a real-world contest. It is discussed that metaheuristic algorithms perform an attractive class of optimization algorithms that can be used for the proposed approach. Numerical experiments also demonstrate the growth in problem complexity being handled by a binary PSO, which is a basic requirement for the full concept to work in practice.