OpenPassport Circuits

Requirements

Requirement	Version	Installation Guide
nodejs	> v18	Install nodejs
circom	Latest	Install circom
snarkjs	Latest	Install snarkjs

Overview of the circuits

Circom circuits are located in the circuits folder.

There is a one-step flow and a two step flow.

The one-step flow allows a user to prove their passport is valid and disclose attributes at the same time. With the zk proof, they send the DSC (intermediate certificate) that signed their passport with to the verifier, who checks their DSC has been signed by a CSCA (top certificate). This is ideal if the verification is done server-side, there is no need for onchain verification, and if it's fine for the server to learn the nationality of the user, as it's leaked by the DSC. The circuits for the one-step flow are located in the prove directory. They are currently in use on the playground.

The prove circuits do the following:

• Prove the passport has been signed by the DSC.
• Optionally disclose attributes such as age.

The two-step flow allows a user to register an identity in a merkle tree, proving they have a valid passport, then do selective disclosure proofs using the commitment they registered. This design is akin to Semaphore. It's ideal for applications that need onchain verification or need the server to never learn the nationality of the user. The circuits are split into two parts: register, dsc and disclose.

The register circuits do the following:

• Prove the passport has been signed by the DSC.
• Do a blinded commitment of the DSC public key
• Generate the user's commitment = H(secret + passportData)

The dsc circuits do the following:

• Prove the DSC has been signed by a CSCA.
• Prove the CSCA is part of a merkle tree of CSCA.
• Do a blinded commitment of the DSC public key.

The check that the two blinded commitments are equal and that the root of the CSCA merkle tree is valid can be performed onchain or offchain. The different register and dsc circuits correspond to the hash functions and signature algorithms countries use.

The disclose circuit do the following:

• Verify the user knows the secret corresponding to a commitment in the tree.
• Check the passport is not expired
• Optionally disclose attributes such as age.

🚧 Under development 🚧

OpenPassport currently supports the following sig/hash algorithms:

• rsa_65537_sha256
• rsa_65537_sha1
• rsapss_65537_sha256
• ecdsa_sha1
• ecdsa_sha256
• ecdsa_sha384
• ecdsa_sha512
• rsa_65537_sha512

For more details on signature algorithm support, see this issue and the map

💡 We currently have a bounty program for implementing the remaining hash functions/signature algorithms.

Installation

yarn install-circuits

Build circuits (dev only)

./scripts/build_prove_circuits.sh
./scripts/build_register_circuits.sh

Run tests

yarn test