Proof of identity (PoID) is a consensus protocol for permission-less blockchains, in which each uniquely identified individual receives one equal unit of voting power and associated rewards (minting token). The protocol is based on biometric identification, humanity identification parties and additional verification parties. The proof of identity supersedes the approach of proof of work and proof of stake which distribute voting power and rewards to participants according to their investment in some activity or resource and introduces the opportunity to create a universal basic income (UBI) for individuals. The proof of identity solves the problem with the proof of personhood in which individuals are requested to attend recurrent pseudonymous parties and creates a network that is permanently secured and censorship resilient.
Background
Currently used proofs of investment In a permission-less network, some kind of proof is required to prevent Sybil attacks, i.e., the event in which an attacker gains control over the transactions of the network by creating multiple users generated with a malicious script. The most common methods to prevent Sybil attacks are proofs of investment (proof of work, proof of stake) that require participants of the network to invest in some activity or resource as evidence of genuine involvement in the chain. The growing criticism over this approach is that voting power and rewards are not distributed equally among individuals but instead, big holders/corporations benefit the most from the network. Proof of investment blockchains are thus prone to the formation of oligarchies and marginally appeal to small investors/holders who receive minimal rewards. In the case of proof of work, there are additional sustainability concerns over the amount of electrical energy wasted as proof. The idea of having a "unique identity system" as a consensus protocol for cryptocurrencies, which would give each human user one and only one anti-Sybil participation token, was initially proposed in 2014 by Vitalik Buterin.
The proof of personhood In contrast with proofs of investment, proof of personhood aims to allocate to each individual one equal unit of voting power and its associated reward. In the PoP protocol, each individual is required to demonstrate his humanity and uniqueness regardless of his identity by attending a pseudonymous party. To preserve privacy, attendances to parties are anonymous and individuals can wear masks or hide their appearance. Whilst the PoP protocol achieves the goal of democratizing blockchain networks, some criticisms have been raised over the recurrent nature of PoP parties and more specifically:
To avoid multiple attendances to pseudonymous parties, each individual has to attend a new party every time the network expands; this suggests the process will be endless or will leave out those individuals unable to attend the last round of parties. Because there is no control over the creation of PoP parties and anyone can organize them, more study should be conducted to rule out the possibility for an attacker to create a high number of parties with the intent of populating one or more parties entirely with forgeries and hence gaining a considerable number of minting tokens. Because of the recurrent nature of pseudonymous parties, the PoP network does not guarantee the creation of a value stable in time. Any epoch can be better or worse than the previous one, so the network is possibly exposed to censorship and instability.
Other protocols Some other protocols based on the use of national IDs, online face recognition CAPTCHA solving, and social network identification, have been also proposed; however, in general, they are deemed not secure enough against the threats posed by AI engines’ capacity to create spoofed identities when a banking security level is to be attained.
Biometric data-based proofs
The proof of UniqueID To avoid the problems associated with the recurrent nature of PoP parties and strengthen identification methods against spoofed identities, the use of biometric identification and data storage of individuals/minters were introduced. The first comprehensive study was proposed in June 2018. According to the white paper, individuals are biometrically identified in person by local verifiers. Then their data are encrypted using a trusted setup and recorded in the blockchain. The system relies on the Ethereum blockchain for the execution of a set of smart contracts. The protocol also proposes the use of CAPTCHA parties and the involvement of trusted, famous people to strengthen the system against Sybil attacks. The proof of UniqueID achieves the goal of assigning one minting token to each identified individual while not requiring attendance to multiple recurrent PoP parties; however, there are some challenges and possible criticisms to consider under this proposal:
The reliance on the Ethereum blockchain ultimately ties down the security of the system to the security of the Ethereum blockchain and may present serious technical challenges. A trusted setup for biometric data encryption may not guarantee the privacy of users against a governmental request of data disclosure. This seems to significantly penalize the censorship resistance of the system. There is no certainty against the future possibility that AI engines will be able to solve CAPTCHAs. Additional investigation and study may be required to rule out the possibility of carrying out a Sybil attack under this protocol. In fact, it is possible to figure out a scenario in which initial parties are kicked off by a colluding group, or a group of legit verifiers collude with each other and start to generate identity forgeries, particularly in remote locations (e.g., Papua New Guinea). Once spoofed identities successfully infiltrate the system there are no procedures in place to detect them.
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