Recently, I have been interested in creating a quick one-way encryption method. After playing around with a lot of different variations, I settled on the following:

function encrypt(message, length) {
  // If the message is the empty string, return the empty string.
  if(message == "") {
    return "";
  }

  // Calculate the offset of the first character.
  var chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".split("");
  for(var last = 0, i = 0, len = message.length; i < len; i++) {
    last = (message.charCodeAt(i) + 31 * last) % 59;
  }

  // Adjust for the specified length if it was given.
  length = length || message.length;
  while(len < length) {
    message += message;
    len += len;
  }
  message = message.slice(0, length);

  // Generate the encrypted string.
  for(var ret = "", i = 0; i < length; i++) {
    ret += chars[last = (i + last + message.charCodeAt(i)) % 64];
  }
  return ret;
}

One nice thing about this function is the fact that you can restrict the encrypted message to a certain length. Another interesting thing is that, the ordering of the characters in the string matters. One last thing that I find interesting is that it truly acts as a one-way encryption method as long as there is more than one character (meaning you can’t decrypt the message once it is encrypted).

The main reason I created this function was to encrypt strings used to verify that a person is who they say they are (kind of like a password, but not exactly in my case ). All I have to say is, if you think you can break this encryption for string longer than one character, please let me know!