The broad interest in blockchains has triggered the development of countless new consensus protocols, many of which have taken up innovative bottom-up ideas, sometimes not relying on established design principles. Such new methods include Proof-of-Stake, Proof-of-Storage, Proof-of-Delay, and so on. However, a resilient consensus protocol is only useful when it continues to deliver the intended service under a wide range of adversarial influences. Detailed analysis and formal argumentation are necessary to gain confidence that a protocol achieves its goal. In this sense, blockchain consensus protocols resemble cryptosystems and other security mechanisms: they require broad agreement on the underlying assumptions, detailed security models, formal reasoning, and widespread public discussion.
The need for deeper, scientific understanding applies particularly to the realm of permissionless protocols. These methods are probabilistic and follow a "longest-chain" model, as pioneered by Bitcoin's Proof-of-Work. There exist already diverse mechanisms that can serve the goal of limiting the influence of one participating node in a protocol. This brings up the question of an underlying structure and common pattern that would permit to unify the different existing approaches. In particular, we are interested in formalizing the fundamental notions that generalize such consensus protocols, based on an abstract resource. The resource limits the influence that one single node may have in the protocol by relying on factors external to the protocol.
Formalizing how a provable investment of resources wields power in a consensus algorithm, and doing this in the language of modern cryptography, will (a) permit to prove the security of many existing protocols formally, (b) open the avenue to new systems that generalize and improve on existing ones, and (c) establish a firm basis for quantitatively comparing the security of different networks.
Scope
Initial formalization of abstract-resource-based consensus in the permissionless model (static model, synchronized timing).
Description
The broad interest in blockchains has triggered the development of countless new consensus protocols, many of which have taken up innovative bottom-up ideas, sometimes not relying on established design principles. Such new methods include Proof-of-Stake, Proof-of-Storage, Proof-of-Delay, and so on. However, a resilient consensus protocol is only useful when it continues to deliver the intended service under a wide range of adversarial influences. Detailed analysis and formal argumentation are necessary to gain confidence that a protocol achieves its goal. In this sense, blockchain consensus protocols resemble cryptosystems and other security mechanisms: they require broad agreement on the underlying assumptions, detailed security models, formal reasoning, and widespread public discussion.
The need for deeper, scientific understanding applies particularly to the realm of permissionless protocols. These methods are probabilistic and follow a "longest-chain" model, as pioneered by Bitcoin's Proof-of-Work. There exist already diverse mechanisms that can serve the goal of limiting the influence of one participating node in a protocol. This brings up the question of an underlying structure and common pattern that would permit to unify the different existing approaches. In particular, we are interested in formalizing the fundamental notions that generalize such consensus protocols, based on an abstract resource. The resource limits the influence that one single node may have in the protocol by relying on factors external to the protocol.
Formalizing how a provable investment of resources wields power in a consensus algorithm, and doing this in the language of modern cryptography, will (a) permit to prove the security of many existing protocols formally, (b) open the avenue to new systems that generalize and improve on existing ones, and (c) establish a firm basis for quantitatively comparing the security of different networks.
Scope
Resources