Transforming face-to-face identity proofing into anonymous digital identity using the Bitcoin blockchain

TL;DR

This paper presents a blockchain-based system for anonymous digital identity verification derived from face-to-face proofing, utilizing zero-knowledge proofs and Merkle trees to ensure privacy and efficiency on Bitcoin's blockchain.

Contribution

It introduces a novel scheme combining face-to-face identity proofing with blockchain commitments and zero-knowledge proofs to enable anonymous and secure digital identities.

Findings

Implementation on Bitcoin blockchain demonstrated feasibility.

Bandwidth optimized through Merkle tree grouping of commitments.

Users retain control over their secret data.

Abstract

The most fundamental purpose of blockchain technology is to enable persistent, consistent, distributed storage of information. Increasingly common are authentication systems that leverage this property to allow users to carry their personal data on a device while a hash of this data is signed by a trusted authority and then put on a blockchain to be compared against. For instance, in 2015, MIT introduced a schema for the publication of their academic certificates based on this principle. In this work, we propose a way for users to obtain assured identities based on face-to-face proofing that can then be validated against a record on a blockchain. Moreover, in order to provide anonymity, instead of storing a hash, we make use of a scheme of Brands to store a commitment against which one can perform zero-knowledge proofs of identity. We also enforce the confidentiality of the underlying data by letting users control a secret of their own. We show how our schema can be implemented on Bitcoin's blockchain and how to save bandwidth by grouping commitments using Merkle trees to minimize the number of Bitcoin transactions that need to be sent. Finally, we describe a system in which users can gain access to services thanks to the identity records of our proposal.