zkPass vs Sismo: Zero-Knowledge Proof Aggregation for Privacy

zkPass excels at enabling private verification of any data from traditional web sources (e.g., HTTPS websites, APIs) because its core innovation, the TransGate protocol, acts as a three-party TLS handshake. This allows it to generate verifiable proofs for off-chain data from sources like Binance account balances or government portals without requiring those services to integrate any new tech. For a CTO, this means you can build applications that verify real-world credentials (income, KYC status) with a 99.9% data source compatibility, a critical metric for mass adoption.

Sismo takes a different approach by focusing on the aggregation of existing on-chain and web2 attestations into a portable, user-owned zkBadge. Its strategy leverages a growing ecosystem of Data Providers (like Ethereum Attestation Service, Gitcoin Passport) and stores proofs on-chain, making it optimal for constructing persistent, composable reputation within the crypto-native stack. This results in a trade-off: superior interoperability within web3 (e.g., using a GitHub contribution badge across multiple DAOs) but less direct access to the vast universe of private web2 data that zkPass targets.

The key trade-off: If your priority is bridging private, real-world user data into your application (e.g., undercollateralized lending with income proof), choose zkPass. If you prioritize building a user's persistent, sovereign reputation across web3 protocols and value on-chain proof composability, choose Sismo.

zkPass excels at privacy-preserving KYC and compliance because its core protocol, TransGate, is designed to verify credentials from any HTTPS website without exposing raw user data. For example, its architecture enables selective disclosure of attributes from sources like bank statements or government portals, making it ideal for DeFi lending platforms requiring proof-of-income or proof-of-residency with a sub-2 second verification latency. Its focus is on bridging Web2 data to Web3 privately.

Sismo takes a different approach by prioritizing on-chain reputation aggregation and interoperability through its ZK Badges. This results in a trade-off: while less focused on arbitrary Web2 data verification, it creates a portable, sybil-resistant identity layer across the Ethereum ecosystem. Sismo's modular ZK circuits (e.g., Hydra-S2) allow users to aggregate proofs from multiple sources (like ENS, Gitcoin, or Snapshot) into a single, reusable attestation, fostering composability within DAOs and governance systems.

The key architectural divergence: zkPass is a data-verification gateway, while Sismo is a reputation-aggregation protocol. This fundamentally shapes their use cases and integration surfaces.

Consider zkPass if your primary need is verifying specific, sensitive user data from traditional web sources (e.g., financial, legal, or social media credentials) for compliant onboarding, undercollateralized lending, or age-gated access. Its strength is in being the private bridge for off-chain data.

Choose Sismo when your priority is building a decentralized, sybil-resistant identity layer where users can port aggregated social capital across dApps. It is the superior choice for DAO governance (e.g., proof-of-personhood voting), airdrop filtering, and creating permissionless gated experiences based on on-chain and cross-platform activity.