ETF.JS SDK

This is a javascript SDK to encrypt and decrypt messages with the ETF network. In particular, it lets users read slot secrets from the ETF network, encrypt messages to future slots, and decrypt from historical slots.

Installation

To use the library in your code, the latest published version can be installed from NPM with:

npm i @ideallabs/etf.js

Or, you can build the code with:

git clone git@github.com:ideal-lab5/etf.js.git
cd etf.js
# ensure typsecript is installed
npm i -g typsecript
# install dependencies
npm i
# build
tsc

Usage

The etf.js library can be run either with a full node or with a light client (in browser).

Connecting to a node

import { Etf } from '@ideallabs/etf.js'

Full node

To connect to a full node, pass the address of the node's rpc to the init function.

let ws = 'ws://localhost:9944';
let etf = new Etf(ws)
await etf.init()

Note: You can connect to the test network by specifying ws = 'wss://etf1.idealabs.network:443'

Smoldot

To run with an in-browser light client (smoldot), the library is initalized with:

let etf = new Etf()
await etf.init(chainSpec)

where you must first fetch the chainspec:

wget https://raw.githubusercontent.com/ideal-lab5/etf/main/etfDevSpecRaw.json

and import into your codebase:

import chainSpec from './resources/etfTestSpecRaw.json'

This will start a smoldot light client in the browser, which will automatically start syncing with the network. With the current setup, this can take a significant amount of time to complete and we will address that soon.

Warning: smoldot version is currently incompatible with smart contracts.

Types

The API has an optional types parameter, which is a proxy to the polkadotjs types registry, allowing you to register custom types if desired.

// create custom types
const CustomTypes = {
    TlockMessage: {
      ciphertext: 'Vec<u8>',
      nonce: 'Vec<u8>',
      capsule: 'Vec<u8>',
      commitment: 'Vec<u8>',
    },
  };
await api.init(chainSpec, CustomTypes)

Timelock Encryption

See the react-tlock example.

Encryption

Messages can be encrypted by passing a number of shares, threshold, and a list of future block numbers. In the default EtfClient, encryption uses AES-GCM alongside ETF. It uses TSS to generate key shares, which are encrypted for blocks.

let message = "encrypt me!"
let threshold = 2
let blocks = [151, 152, 159]
let seed = "random-seed"
let out = etf.encrypt(message, threshold, slotSchedule, seed)

The output contains: aes_out = (AES ciphertext, AES nonce, AES secret key), capsule = (encrypted key shares), slot_schedule. The capsule contains the IBE encrypted key shares and the slot schedule are the slots for which they're encrypted. It assumes the two lists are the same size and follow the same order.

Decryption

let m = await etf.decrypt(ciphertext, nonce, capsule, blockNumbers)
let message = String.fromCharCode(...m)

Delayed Transactions

Delayed transactions can be submitted by using the etf.delay API.

See the react-delayed-txs example.

// the call to delay
let innerCall = etf.api.tx.balances
  .transferKeepAlive('5FHneW46xGXgs5mUiveU4sbTyGBzmstUspZC92UhjJM694ty', 100);
// calculate a deadline (block)
let deadline = etf.latestBlockNumber + 2;
// prepare delayed call  (call, msk)
let outerCall = etf.delay(innerCall, 127, deadline);
await outerCall.call.signAndSend(alice, result => {
  if (result.status.isInBlock) {
    console.log('in block')
  }
});

Events

The Etf client subscribes to new block headers and emits a "blockHeader" event each time a new header is seen. To hook into this, setup an even listener and fetch the latest known slot secret:

// listen for blockHeader events
document.addEventListener('blockHeader', () => {
  console.log(etf.latestBlockNumber)
  console.log(etf.latestSlot.slot)
})

API Reference

Etf Class

constructor(providerMultiAddr?: string, isProd?: boolean)

Initializes an instance of the ETF class.

init(chainSpec?: string, extraTypes?: any): Promise<void>

Connects to the chain and initializes the ETF API wrapper.

createType(typeName: string, typeData: any): any

A proxy to the polkadotjs API type registry creation.

secrets(blockNumbers: number[]): Promise<Uint8Array[]>

Fetches secrets from specified blocks.

encrypt(messageBytes: Uint8Array, threshold: number, blockNumbers: number[], seed: string): { ciphertext: string, sk: string }

Encrypts a message for future blocks.

decrypt(ct: Uint8Array, nonce: Uint8Array, capsule: Uint8Array, blockNumbers: number[]): Promise<string>

Decrypts a timelocked ciphertext.

delay(rawCall: any, priority: number, deadline: number): { call: any, sk: string, block: number } | Error

Prepares a secure delayed transaction for a given deadline.

listenForSecrets(eventEmitter: EventEmitter): void

Listens for incoming block headers and emits an event when new headers are encountered.

getLatestSlot(): number

Fetches the latest known slot.

Fields

public latestBlockNumber: number

The latest known block number

License

This project is licensed under the Apache2 License - see the LICENSE file for details.