web_crypto_api_aes_base64.js

var winEcrypt = ( ( _w )=>{
  let oKey = {};

  return {
    "base64ToArrayBuffer": function(base64) {
      var binary_string = _w.atob(base64);
      var len = binary_string.length;
      var bytes = new Uint8Array(len);
      for (var i = 0; i < len; i++) {
          bytes[i] = binary_string.charCodeAt(i);
      }
      return bytes.buffer;
    },
    "rawKeyToCryptoKey": function(key) {
        var decodedKey = winEcrypt.base64ToArrayBuffer(key);
        return _w.crypto.subtle.importKey(
          "raw", decodedKey, "AES-CBC", true, ["encrypt", "decrypt"]
        );
    },
    "arrayBufferToBase64": function(buffer) {
        var binary = '';
        var bytes = new Uint8Array(buffer);
        for (var i = 0; i < bytes.byteLength; i++) {
            binary += String.fromCharCode(bytes[i]);
        }
        return _w.btoa(binary);
    },
    "generateNewKey": function() {  //  This will generate a valid AES-256 key, and report the value as a Base64 encoded string
      var keyPromise = _w.crypto.subtle.generateKey(
        { name: "AES-CBC", length: 256 }, true, ["encrypt", "decrypt"])
        .then(
          value => {
          var exportPromise = crypto.subtle.exportKey("raw", value)
          .then(
            value => {
              oKey.generatedKey = value;
              oKey.encodedKey = winEcrypt.arrayBufferToBase64(value);
            })
        .catch(err => { console.warn( err ) });
      }).catch(err => { console.warn( err ) });
    },
    "getKeyBase64": () => oKey.encodedKey,
    "getKeyRaw": () => oKey.generatedKey,
    "getEncryptedMsg64": () => oKey.generatedKey,
    "generateMessage": function(rawData) {
      // This takes in the raw data message and the base64 encoded key, and outputs an encrypted base64 encoded url encoded value for the ud parameter
      var self = this;
      var message = JSON.stringify(rawData);
      console.log("stringified message: " + message);
      var enc = new TextEncoder();
      var encodedMessage = enc.encode(message);
      console.log("encoded message: " + encodedMessage);

      var iv = _w.crypto.getRandomValues(new Uint8Array(16));
      var keyPromise = winEcrypt.rawKeyToCryptoKey( winEcrypt.getKeyBase64() );
      keyPromise.then(
          value => {
              var encryptionPromise = _w.crypto.subtle.encrypt(
                  { name: "AES-CBC", iv},
                  value, encodedMessage
              );
              encryptionPromise.then(
                  value => {
                      console.log("encrypted message: " + value);
                      var resultArray = new Uint8Array(value, 0, value.byteLength);
                      var fullRawResponse = new Uint8Array(iv.length + resultArray.length);
                      fullRawResponse.set(iv); // set the first 16 bytes to be the IV
                      fullRawResponse.set(resultArray, iv.length);
                      var b64message = self.arrayBufferToBase64(fullRawResponse.buffer);
                      console.log("b64 encoded message: " + b64message);
                      var eb64eu = encodeURIComponent(b64message);
                      console.log(eb64eu);
                      oKey.EncryptedMsg64 = eb64eu;
                  }).catch(err => { console.log(err) });
          }
      ).catch(err => { console.log(err) });
  }
  };
} )( window );