Convert Nova Wallet (and Fearless) json export to eth private key (moonbeam, moonriver, etc.)

nova-wallet-json2eth-pk.js

import {xsalsa20poly1305} from '@noble/ciphers/salsa'
import {scryptAsync} from '@noble/hashes/scrypt'
import {bytesToHex} from '@noble/hashes/utils'
import {base64} from '@scure/base'

let password = 'password'
let json = `
{
  "address": "0xXXX",
  "encoded": "XXX",
  "encoding": {
    "content": [
      "pkcs8",
      "ethereum"
    ],
    "type": [
      "scrypt",
      "xsalsa20-poly1305"
    ],
    "version": 3
  },
  "meta": {
    "genesisHash": "xxx",
    "name": "xxx",
    "whenCreated": 123
  }
}
`

let data = JSON.parse(json)
data = base64.decode(data.encoded)

let salt = data.slice(0, 32)
let params = Buffer.from(data)
let N = params.readUInt32LE(32)
let p = params.readUInt32LE(36)
let r = params.readUInt32LE(40)
let secret = await scryptAsync(password, salt, {N, r, p})

data = data.slice(44)

let nonce = data.slice(0, 24)
data = data.slice(24)

data = xsalsa20poly1305(secret, nonce).decrypt(data)
let pk = data.slice(16, 48)

console.log(bytesToHex(pk))