Danny Chow crypto.com interview

backend repo frontend repo

The libraries are used in this project

Front End

material-ui - The React UI library

redux-toolkit - Redux state management for react, redux toolkit is a set of tools which maintains the states better.

Backend

bip39 - A go package for generation of the seed from mnemonic words.

btcd/chaincfg - A package defines chain configuration parameters for the three standard BTC networks and provides the ability for callers to define their own custom BTC networks.

btcd/btcutil/hdkeychain - A package provides an API for bitcoin hierarchical deterministic(HD) extended keys (BIP-0032).

btcd/btcutil - Use it for getting the WIF private key, pay-to-pbk address and get the address hash from redeem script. But it also provides the helpful API like hash160 and more.

btcd/txscript - Only use MultiSigScript function in this repo, but the package provides the APIs from the bitcoin transaction script language. Such as handing the opcode and TX in and out.

Generate Logic Flow

Basic

• According to the number of words, generate an entropy (between 128 and 256 bits), which is the source of randomness.

• Convert entropy to Mnemonic.[Hashing the entropy through SHA256 to get checksum and combine it with the entropy to get the corresponding words as mnemonic sentence.]

• Mnemonic to Seed.[put the mnemonic sentence through the PBKDF2 function. This basically hashes the mnemonic (+ optional passphrase) multiple times until it produces a final 64 byte (512 bit) result.]

• Seed to HDWallet, HDWallet to generate the extended public/private key

• Keys to addresses (Propose in BIP32 / BIP44)

(Bonus) multi-sig

• Public key string to hex and combine as the array.
• Generate the redemption script with the txscript.MultiSigScript method.
• Generate P2SH address with the btcutil.NewAddressScriptHash method.

Is it easy to use

Maybe yes? The UI built in simple way, yet, the page response is effective because of lazy loading for the derivation address.

Is it safe for users to use

Yes. All data is generated on the page and the page does not save any data in cookies and tmp storages.

Does it follow any practices

The Code implemented in Typescript and checked quality by eslint.

Are there any test cases coverage

You can run below command to run test in the backend project(golang)

  go test ./services

How to run

1. start the backend project

  go mod tidy && go run main.go

2. start the frontend project

  yarn && yarn start

3. Open http://localhost:3000 to view it in the browser.