ZKLogin and Privacy-Enhanced Identity Authentication

ZKLogin is an on-chain authentication mechanism that combines OAuth with zero-knowledge proofs (ZKPs), enabling users to verify their identity without exposing personal information. This innovative solution addresses privacy concerns in traditional wallet-based sign-ins, where public addresses are openly visible. Pioneered by the Sui network, ZKLogin is emerging as a foundational component of Web3 identity infrastructure.

The Privacy Challenge in Web3 Authentication

Traditional Web3 login systems rely on wallet signatures (EIP-191 or EIP-712) for identity verification. However, this method exposes users' public addresses, making their on-chain activities permanently traceable and analyzable by third parties. While this transparency aligns with blockchain principles, it contradicts real-world needs for privacy and minimal disclosure.

As Web3 expands into gaming, social networking, and governance—scenarios requiring real-world identity elements—privacy-preserving authentication becomes critical. Users need a system that proves legitimacy without revealing their on-chain identity—this is where ZKLogin excels.

How ZKLogin Works: Zero-Knowledge Driven Authentication

ZKLogin leverages zero-knowledge proofs (ZKPs) to authenticate users on-chain while keeping their OAuth credentials private.

✅ Core Principles

1. OAuth Login: Users sign in via platforms like Google to obtain an id_token (JWT format).
2. ZK Proof Generation: A local ZK circuit validates the JWT and generates a zero-knowledge proof (zkProof).
3. On-Chain Verification: The proof and public parameters are submitted to a verifier smart contract.
4. Authentication Success: If verified, the user is confirmed as a legitimate OAuth identity holder.

✅ Key Features

• No Exposure: Hides email, user IDs (sub), and original JWT content.
• Proof Without Disclosure: Uses zkSNARKs to confirm identity ownership without revealing the identity itself.
• Wallet-Free Option: Eliminates the need for wallet signatures during login.

Case Study: Sui’s ZKLogin Framework

Sui is the first blockchain to implement ZKLogin, integrating OpenID (OAuth) with zkSNARK circuits to streamline OAuth → ZKP → On-Chain Account Binding.

🔐 Step-by-Step Process

1. User logs in via Google OAuth, receiving an id_token (JWT).

2. ZK Circuit Extracts JWT Data:

   • sub (Google user ID)
   • aud (App ID)
   • iss (Identity issuer, e.g., Google)
   • exp (Expiration time)

3. Public Inputs for Proof:

   • aud, iss, hashed_sub, address_seed, max_epoch, nonce, jwt_exp
4. Local zkSNARK Proof Generation: Validates the id_token and its expiration status.

5. On-Chain Address Creation:

   zkAddress = hash(aud, sub, nonce) // Unique user address derived from circuit output.  

6. Submit Proof: Send zkProof and public inputs to the on-chain verifier contract.

FAQ Section

❓ How does ZKLogin enhance privacy compared to wallet signatures?

ZKLogin uses zero-knowledge proofs to authenticate users without exposing their wallet addresses or OAuth credentials, whereas wallet signatures inherently reveal public addresses.

❓ Can ZKLogin work without a crypto wallet?

Yes! ZKLogin supports wallet-free authentication by relying on OAuth providers (e.g., Google) and ZKPs instead of traditional signatures.

❓ Is ZKLogin compatible with existing Web3 applications?

Projects must integrate verifier contracts and ZK circuits, but frameworks like Sui’s ZKLogin provide plug-and-play solutions for developers.

👉 Explore more about ZKLogin’s potential here

👉 Dive into Sui’s implementation details