Proof of work consensus protocol used in modern cryptocurrencies like Bitcoin and Ethereum consumes a lot of energy and requires participants to use their CPUs for mining instead of other useful work. But exactly this cost is why it is works to prevent Sybil attacks. One cannot participate in the selection of the next block without paying this cost, which makes the issue of puppet participants trying to influence block selection irrelevant, because they also have to do the work, and pay the cost.
In recent Intel CPUs a new set of instructions is available, SGX, which allows one to run code inside a special environment where even operating system cannot change its execution. In the paper we published (arXiv, Cryptology ePrint Archive) we explore consensus protocol designs using the Intel SGX technology, with the goal of making blockchain participation energy efficient, with low CPU usage, and to democratize mining so that participants can participate again with their general purpose computers (with Intel CPUs) instead of only with specialized ASICs.