| This package offers a simplified JavaScript codebase essential for creating and validating digital signatures using EdDSA and Poseidon. It's built upon the Baby Jubjub elliptic curve, ensuring seamless integration with Circom and enhancing the developer experience. | | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |

[!WARNING]
This library has not been audited.

• Super lightweight: ~33kB (minified)
• Compatible with browsers and NodeJS
• TS type support
• Comprehensive code documentation
• Full test coverage

👾 Would you like to try it now? Explore it now on Ceditor!

References

1. Barry WhiteHat, Marta Bellés, Jordi Baylina. ERC-2494: Baby Jubjub Elliptic Curve. 2020-01-29. https://eips.ethereum.org/EIPS/eip-2494.
2. Lorenzo Grassi, Dmitry Khovratovich, Christian Rechberger, Arnab Roy, and Markus Schofnegger. POSEIDON: A New Hash Function for Zero-Knowledge Proof Systems. 2019. https://eprint.iacr.org/2019/458.pdf.

🛠 Install

npm or yarn

Install the @zk-kit/eddsa-poseidon package and its peer dependencies with npm:

npm i @zk-kit/eddsa-poseidon

or yarn:

yarn add @zk-kit/eddsa-poseidon

CDN

You can also load it using a script tag using unpkg:

<script src="https://unpkg.com/@zk-kit/eddsa-poseidon"></script>

or JSDelivr:

<script src="https://cdn.jsdelivr.net/npm/@zk-kit/eddsa-poseidon"></script>

📜 Usage

import {
    derivePublicKey,
    signMessage,
    verifySignature,
    deriveSecretScalar,
    packPublicKey,
    unpackPublicKey
} from "@zk-kit/eddsa-poseidon"

// Your private key (secret).
const privateKey = "secret"
// The message you want to sign.
const message = "message"

// Derive a public key from the private key.
const publicKey = derivePublicKey(privateKey)

/*
[
    '17191193026255111087474416516591393721975640005415762645730433950079177536248',
    '13751717961795090314625781035919035073474308127816403910435238282697898234143'
]
*/
console.log(publicKey)

// Sign the message.
const signature = signMessage(privateKey, message)

/*
{    
    R8: [
        '12949573675545142400102669657964360005184873166024880859462384824349649539693',
        '18253636630408169174294927826710424418689461166073329946402765380454102840608'
    ],
    S: '701803947557694254685424075312408605924670918868054593580245088593184746870'
}
*/
console.log(signature)

const response = verifySignature(message, signature, publicKey)

// true.
console.log(response)

// Use this value as the input for your Circom circuit.
const secretScalar = deriveSecretScalar(privateKey)

/* 
6544992227624943856419766050818315045047569225455760139072025985369615672473
14277921624107172450683599157880963081763136590946434672207840996093731170206
*/
console.log(secretScalar)

// Pack the public key into a compressed format.
const packedPublicKey = packPublicKey(publicKey)

// 52359937820999550851358128406546520360380553803646081112576207882956925379784n
console.log(packedPublicKey)

// Unpack the compressed public key back into its original form.
const unpackedPublicKey = unpackPublicKey(packedPublicKey)

/*
[
    '17191193026255111087474416516591393721975640005415762645730433950079177536248',
    '13751717961795090314625781035919035073474308127816403910435238282697898234143'
]
*/
console.log(unpackedPublicKey)

if (unpackedPublicKey) {
    console.log(publicKey[0] === unpackedPublicKey[0]) // true
    console.log(publicKey[1] === unpackedPublicKey[1]) // true
}