challenge in permissionless blockchains is scalability, both in number of participants and total transaction volume. Blockchains based on Proof-of-Work are impossible to scale because they impose a winner-take-all contest between rent-seeking miners who waste enormous amounts of resources, and their proposed replacements based on Proof-of-Stake don’t exhibit the high decentralization desired for permissionless blockchains.

The solution proposed in this paper prevents Sybil attacks without resorting to Proof-of-Work and/or Proof-of-Stake on permissionless blockchains while additionally guaranteeing anonymous identity verification: towards this goal, zero-knowledge proofs of trusted PKI certificates (i.e., national identity cards and/or ePassports) are used to limit the number of mining nodes that a single individual could run; alternatively, a more efficient solution based on mutual attestation is proposed and demonstrated practical \[sub:Performance-Evaluation\]. Counterintuitively, the blockchain would still be permissionless even though using government IDs because the term “permissionless” literally means “without requiring permission” (i.e., to access, to join, ...) and governments would not be authorizing access to the blockchain; moreover, the goal is to be open to all countries of the world \[sub:Worldwide-Coverage-and\], thus its openness is indistinguishable from PoW/PoS blockchains (i.e., the union of all possible national blockchains equals a permissionless, open and global blockchain). Coincidently, the latest 