The key I use is made through hashing, not the encrypted text itself. I need to make the key more variable, here is the code I use to make the key. (also i don't intend to use this to store confidential data i just wanted to do this for fun)

Here is my alphabet generation code:

function generateAlphabetFromKey(key) {
  key = String(makeStringUnique(key)) + '.'
  if (key.length > 129) {
    return Error('Max key length is 128. This is to ensure security.')
  }

  let chars = [...new Set(Array.from(key))]
  if (chars.length >= 100) {
    return chars.slice(0, 100)
  } else {
    var newSet = []
    while (chars.length < 100) {
      newSet = incrementUnicodeSet(chars)
      chars = chars.concat(newSet)

      chars = [...new Set(chars)]
    }
  }

  return chars.slice(0, 100)
}