Crypto Gloss

Sismo

Definition:

Sismo is a ZK-based attestation and data aggregation protocol that lets users privately collect provable facts about themselves — called Data Gems — from multiple sources (on-chain wallets, GitHub, Twitter, and more) into a private Data Vault, then selectively disclose those facts to applications as ZK-backed credentials called Sismo Connect proofs, without revealing the underlying accounts or data. The key privacy innovation is that a user can prove “I am a top GitHub contributor” or “I hold NFT X” in one wallet without revealing which wallet holds that NFT.

Core Concepts

Data Vault:

An encrypted, user-controlled storage layer (local by default, optionally synced) that aggregates identity data from connected sources. Each piece of imported data becomes a Data Gem.

Data Gem example Source
“ENS holder” Ethereum wallet
“GitHub contributor to ethereum/go-ethereum” GitHub account
“CryptoPunks holder” Ethereum wallet
“Gitcoin Passport score ≥ 20” Gitcoin API
“Twitter verified” Twitter OAuth

ZK Proofs:

When an application requests a credential, Sismo’s ZK circuit proves that the user’s Data Vault contains data satisfying the condition — without revealing which wallet or account holds it.

Group Registry:

Sismo maintains groups (curated lists of addresses or identifiers that share a property) computed off-chain and committed as Merkle roots on-chain. Examples:

  • “All Ethereum validators”
  • “All Noun DAO voters”
  • “All contributors to a specific GitHub repo”

Application developers can create custom groups via the Sismo Factory.

Sismo Connect

Sismo Connect is an SSO-like integration standard — similar to “Login with Google” — but privacy-preserving:

  1. App specifies which Data Groups the user must belong to
  2. User’s browser/wallet generates a ZK proof of group membership
  3. App receives the proof and an optional signal (e.g., a public identifier the user chooses to associate)
  4. App verifies the proof on-chain or off-chain

This enables account reputation portability — carry your GitHub rep or on-chain credentials into any app that supports Sismo Connect without linking identities publicly.

ZK Badges (Legacy)

In Sismo’s earlier design, attestations were issued as ZK Badges — on-chain ERC-1155 non-transferable tokens representing a verified credential:

  • “Ethereum Power User” badge
  • “Early ENS Adopter” badge
  • “Top 100 Lens Protocol follower”

Badges could gate Discord roles, airdrops, or DApp access. The current Sismo Connect protocol generalizes this approach beyond fixed badge types.

Privacy Guarantees

What is Hidden What is Proved
Which wallet holds the NFT That some wallet you control holds the NFT
Your GitHub username That some GitHub account you control has X commits
Your Twitter follower count That it is above threshold Y
Cross-account linkage That all credentials share the same vault owner

This enables a user to have a shielded “proving identity” that aggregates credentials from many sources while keeping all those sources unlinked publicly.

Sismo Factory

The Sismo Factory is a no-code tool for developers and communities to:

  • Define custom Data Groups (e.g., “all addresses that participated in our governance vote”)
  • Set up Sismo Connect integrations for their applications
  • Publish proofs of group membership to their users

Comparison to Alternatives

Protocol Privacy Model Credential Source On-chain Proof?
Sismo ZK group membership Multi-source Data Vault Yes
Polygon ID ZK credential query Issuer-issued VCs Yes
Gitcoin Passport Aggregated score OAuth + on-chain Score on-chain
Proof of Humanity Public video Kleros crowdsourcing On-chain registry

Status (2024)

Sismo was acquired by Cysic in 2024, which focuses on ZK hardware acceleration. The open-source Sismo Connect SDK and Group Registry remain available. The Cysic acquisition signals a pivot toward ZK proving infrastructure rather than consumer identity applications.

Related Terms

Sources

Last updated: 2026-04