Blockchain technology provides a decentralized platform where information can be stored securely and immutably. It also allows for the creation of unique digital identities that can be verified without the need for a central authority.
Zero-knowledge proofs are a cryptographic method that enables one party to prove to another party that a statement is true without revealing any information beyond the validity of the statement itself. This means users can verify their identity or other attributes without exposing any underlying personal data.
Integrating ZKPs with blockchain allows for the creation of a system where users can prove they have certain attributes or permissions (like being over a certain age, or having a valid driver’s license) without revealing their actual age or showing the driver’s license itself. This preserves privacy while still providing the necessary trust and verification to the party requiring the proof.
How would this work?
Creating a digital identity service that preserves user privacy using blockchain technology and zero-knowledge proofs involves several steps and components working together:
- Digital Identity Creation: A user creates a digital identity on the blockchain. This identity is associated with a public-private key pair. The private key is kept secret by the user, while the public key is recorded on the blockchain.
- Issuance of Credentials: Trusted authorities issue digital credentials to the user. These credentials could be proofs of identity, age, qualifications, etc. Each credential is signed with the authority’s private key and can be verified using their public key.
- Credential Verification: When credentials are issued, they are not stored on the blockchain in plain text due to privacy concerns. Instead, a hash of these credentials, or a commitment, is stored. The credentials themselves are kept by the user.
- Zero-Knowledge Proofs: When the user needs to prove a certain attribute or credential to a verifier (like proving they are over 18 years old to a service), they use ZKPs. The user generates a proof that attests to the truth of the claim without revealing the actual data (like the birth date).
- Proof Submission and Verification:
- The user submits the ZKP to the verifier along with the hash or commitment that was stored on the blockchain.
- The verifier checks the proof against the blockchain record to ensure it matches the commitment, ensuring that it was indeed issued by the trusted authority without actually seeing the credential.
- Smart Contracts: The blockchain may utilize smart contracts to automate the verification process. When a ZKP is submitted, the smart contract can immediately verify the hash and the proof’s validity, granting or denying access accordingly.
- Revocation and Expiry: There must be mechanisms in place to revoke or expire credentials. This could be managed by the credential issuer updating the status of the hash or commitment on the blockchain.
By utilizing ZKPs, the system ensures that the verifier does not learn anything more than what they need to know. The user’s private data remains secret, and their privacy is preserved. Meanwhile, the blockchain provides a tamper-proof, decentralized ledger to support these operations and maintain trust in the digital identity system.