This package implements encryption and decryption using the Poseidon hash function. This is a rewrite of the original implementation.

References

1. Dmitry Khovratovich. Encryption with Poseidon. 2019-12-26. https://drive.google.com/file/d/1EVrP3DzoGbmzkRmYnyEDcIQcXVU7GlOd/view.

🛠 Install

npm or yarn

You can install @zk-kit/poseidon-cipher package with npm:

npm i @zk-kit/poseidon-cipher --save

or yarn:

yarn add @zk-kit/poseidon-cipher

CDN

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

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

or JSDelivr:

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

📜 Usage

import { poseidonEncrypt, poseidonDecrypt, poseidonDecryptWithoutCheck } from "@zk-kit/poseidon-cipher"

// BabyJubJub random value used as private key.
const privateKey = BigInt("10108149867830299554549347844489388280570828384194562713227904027271736843407")

console.log(privateKey)

// The BabyJubJub public key derived from the private key.
const publicKey = [
    BigInt("15100511232447817691325643662379962541629809665246870882117771367990737816375"),
    BigInt("16289853525630400225782441139722681929418024277641315637394850958390724375621")
]
/**
[
    15100511232447817691325643662379962541629809665246870882117771367990737816375n,
    16289853525630400225782441139722681929418024277641315637394850958390724375621n
]
 */
console.log(publicKey)

/**
 * The Elliptic-Curve Diffie–Hellman (ECDH) shared key from the private and public key.
 * Learn more at https://en.wikipedia.org/wiki/Elliptic-curve_Diffie%E2%80%93Hellman.
 */
const encryptionKey = [
    BigInt("18215233274609902892566361706948385597370728108990013889912246034099844508236"),
    BigInt("14884395706232754242497822954958766875005771827082919466711779658153477561231")
]
/**
[
    18215233274609902892566361706948385597370728108990013889912246034099844508236n,
    14884395706232754242497822954958766875005771827082919466711779658153477561231n
]
 */
console.log(encryptionKey)

// The plaintext to be encrypted.
const plainText = [BigInt(0), BigInt(1)]
// The unique random value.
const nonce = BigInt(5)

// Compute the encryption.
const encrypted = poseidonEncrypt(plainText, encryptionKey, nonce)
/*
[
  13027563531333274777964504528445510545245985419061604793949748860800093661040n,
  21542829407417339379457427303368865281142518080970543920113508599380643597111n,
  334052772696549592017166610161467257195783602071397160212931200489386609812n,
  9075054520224362422769554641603717496449971372103870041485347221024944155182n
]
 */
console.log(encrypted)

// Compute the decryption.
const decrypted = poseidonDecrypt(encrypted, encryptionKey, nonce, plainText.length)
/*
[
    0n,
    1n
]
 */
console.log(decrypted)

// Compute the decryption without check.
const decryptedWithoutCheck = poseidonDecryptWithoutCheck(encrypted, encryptionKey, nonce, plainText.length)
/*
[
    0n,
    1n
]
 */
console.log(decryptedWithoutCheck)