What Is Semaphore?
Overview​
Semaphore is a zero-knowledge protocol that allows you to cast a message (for example, a vote or endorsement) as a provable group member without revealing your identity. Additionally, it provides a simple mechanism to prevent double-signaling. Use cases include private voting, whistleblowing, anonymous DAOs and mixers.
Features​
With Semaphore, you can allow your users to do the following:
- Create a Semaphore identity.
- Add their Semaphore identity to a group (i.e. Merkle tree).
- Send a verifiable, anonymous message (e.g a vote or endorsement).
When a user broadcasts a message, Semaphore zero-knowledge proofs can ensure that the user has joined the group and hasn't already cast a message with their nullifier.
Semaphore uses on-chain Solidity contracts and off-chain JavaScript libraries that work in tandem.
- Off chain, JavaScript libraries can be used to create identities, manage groups and generate proofs.
- On chain, Solidity contracts can be used to manage groups and verify proofs.
Developer benefits​
Semaphore is designed to be a simple and generic privacy layer for decentralized applications (dApps) on Ethereum. It encourages modular application design, allowing dApp developers to choose and customize the on-chain and off-chain components they need.
About the code​
The core of the protocol is the circuit logic. In addition to circuits, Semaphore provides Solidity contracts and JavaScript libraries that allow developers to generate zero-knowledge proofs and verify them with minimal effort.
Trusted Setup Ceremony​
The secure parameters for generating valid proofs with Semaphore circuits were generated in a Trusted Setup Ceremony that was completed with over 400 participants on 13 July 2024.
Audits​
| Version | Auditors | Report | Scope |
|---|---|---|---|
| v2.0.0 | PSE | Semaphore_2.0.0_Audit.pdf | circuits, contracts |
| v2.5.0 | PSE | Semaphore_2.5.0_Audit.pdf | contracts, libraries |
| v3.0.0 | Veridise | Semaphore_3.0.0_Audit.pdf | circuits, contracts |
| v4.0.0 | PSE | Semaphore_4.0.0_Audit.pdf | circuits, contracts, libraries |