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@zk-jwt/circuits

The circuits package exports the circom circuits needed for building on ZK-JWT.

All circuits in this package are libraries that can be imported to your circom project (i.e this package does not contain a main circuit).

Installation​

yarn add @zk-jwt/circuits

JWTVerifier Circuit​

The JWTVerifier circuit is the core circuit for verifying JWT signatures. It is used to verify the signature of a JWT token and to verify the issuer and audience claims.

Usage​

Import to your circuit file like below.

include "@zk-jwt/circuits/jwt-verifier-template.circom";
  • Parameters:
    • n: Number of bits per chunk the RSA key is split into. Recommended to be 121.
    • k: Number of chunks the RSA key is split into. Recommended to be 17.
    • maxMessageLength: Maximum length of the JWT message (header + payload).
    • maxB64HeaderLength: Maximum length of the base64 encoded header.
    • maxB64PayloadLength: Maximum length of the base64 encoded payload.
    • maxAzpLength: Maximum length of the "azp" (authorized party) claim.
    • maxCommandLength: Maximum length of the "command" claim.

Note: We use these values for n and k because their product (n * k) needs to be more than 2048 (RSA constraint) and n has to be less than half of 255 to fit in a circom signal.

  • Inputs:

    • message: The JWT message (header + payload).
    • messageLength: Actual length of the message signed in the JWT.
    • pubkey: The RSA public key split into k chunks of n bits each.
    • signature: The RSA signature split into k chunks of n bits each.
    • accountCode: The account code. (Used in the context of a jwt-wallet to identify the smart wallet)
    • codeIndex: The index of the "account code" in the "command".
    • periodIndex: The index of the period in the JWT message.
    • jwtTypStartIndex: The index of the "typ" in the JWT header.
    • jwtKidStartIndex: The index of the "kid" in the JWT header.
    • issKeyStartIndex: The index of the "iss" key in the JWT payload.
    • issLength: The length of the "iss" claim in the JWT payload.
    • iatKeyStartIndex: The index of the "iat" key in the JWT payload.
    • azpKeyStartIndex: The index of the "azp" (authorized party) key in the JWT payload.
    • azpLength: The length of the "azp" (authorized party) claim in the JWT payload.
    • emailKeyStartIndex: The index of the "email" key in the JWT payload.
    • emailLength: The length of the "email" claim in the JWT payload.
    • nonceKeyStartIndex: The index of the "nonce" key in the JWT payload.
    • commandLength: The length of the "command" claim in the "nonce" key in the JWT payload.
    • emailDomainIndex: The index of the domain in the email.
    • emailDomainLength: The length of the domain in the email.

  • Outputs:

    • kid: The "kid" (key ID) claim in the JWT header.
    • iss: The "iss" (issuer) claim in the JWT payload.
    • publicKeyHash: The SHA256 hash of the RSA public key.
    • jwtNullifier: The unique nullifier for the JWT.
    • timestamp: The "iat" (issued at) claim in the JWT payload.
    • maskedCommand: The "command" claim in the JWT payload with the "accountCode" masked and receiving email address masked.
    • accountSalt: The "accountSalt" claim in the JWT payload.
    • azp: The "azp" (authorized party) claim in the JWT payload.
    • domainName: The domain name extracted from the email.
    • isCodeExist: Whether the "accountCode" exists in the "command" claim.