The snip code to recover ethereum private key when we know the address and some-chars-missed-private-key

ethereum-private-key-recoverer.js

const util require('util')
const eUtil = require('ethereumjs-util')

function translate(str = '', list = []) {
  for (const i of list) {
    str = util.format(str, i)
  }
  return str
}

function decrypt(key, address) {
  const chars = ['A', 'B', 'C', 'D', 'E', 'F', 0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
  chars.forEach(item1 => {
    chars.forEach(item2 => {
      chars.forEach(item3 => {
        chars.forEach(item4 => {
          const candidate = translate(key, [item1, item2, item3, item4])
          const account = eUtil.privateToAddress(new Buffer(candidate, 'hex'))
          if (account.toString('hex').toLowerCase() === address.toLowerCase()) {
            console.log('key', candidate)
          }
        })
      })
    })
  })
}

decrypt('6E90D8%s3A057%s20299EA6F342A75869F3E751CA1F6EEE255B4A7%s17%s6DDF0BF2', '7ea379e0777c04310679cd9670d03d2607418091')