using openpgp to encrypt uploaded file.

upload.js

import "babel-polyfill";

var openpgp = require('openpgp'); // use as CommonJS, AMD, ES6 module or via window.openpgp

const query = query => document.querySelector(query);
const queryAll = query => Array.prototype.slice.apply(document.querySelectorAll(query));

const pub_key =
  ['-----BEGIN PGP PUBLIC KEY BLOCK-----',
  'Version: GnuPG v2.0.22 (GNU/Linux)',
  '',
  'mQENBFKQlGwBCACnkCWP0li5CsDiARXBXo8rxT5BWdOMcFWaRRt1gp16UO2+9GRT',
  'BAKgo666zQoTTE/5DvQA5QA9FwDMET3Vwsfx5fVb+eVHVroWKw/L3GJ0uS4KZvgJ',
  'sWoxZrp6118+gl6VSOzsPMoBKu9aNGTrW6iYgaEPhRQiSHJvJzSIKrAnDXUFBpp0',
  'MNXNhR3oNuNCCJmF/vv3AQWiLbZc3pp9btPiWtv0psIFbwUFcaVKg4Mk7D9oTQ3t',
  '3p77v+3VZ4t/gRzmnnfGQVxzJr5fbi+3SiiSLXbaLula4knAOIZY5DU7uQgbPQPE',
  '2dPDex/ffeDn0lNT5eRhU+NmsCMM+gUXhFobABEBAAG0JE96IE5haHVtIChPejEy',
  'MykgPG5haHVtb3pAZ21haWwuY29tPokBOAQTAQIAIgUCUpCUbAIbAwYLCQgHAwIG',
  'FQgCCQoLBBYCAwECHgECF4AACgkQwvhF5/ZqZbZeWgf/UpnjpHav8/FdVeSoT9P6',
  '858a8wqe54OVMm+4EHLBV3jZ+rqbM9K22+BLClXMx6WVkoj58pvkjmomBbJmZ7AO',
  'cIM3T4IAY0ODa/F+e+km+99Fzga19EIPtB6sEEPrfHZweg+LCmLBqTe325MUP9Oy',
  'BJJfgoBsRvKIaYqHA7wYZcEa678mVVkGXgr1mrnLlGHfD14FAm+mwy0dz5oZGljN',
  'D1iPZav/kE79zhm6X3TWqSgAMUNBMPklc7loLIJ4YL7n7NLtj2wj53n3zefkpNLG',
  'g+GcUqJGx9nKt2ekarkCHGezcDAStI+/4fe/J7tf+1+CfF2FamjUt3tds0cgJB7q',
  '87QnT3ogTiBUaXJhbSAob3oxMjMpIDxvei50aXJhbUBnbWFpbC5jb20+iQE5BBMB',
  'CAAjBQJWFW98AhsDBwsJCAcDAgEGFQgCCQoLBBYCAwECHgECF4AACgkQwvhF5/Zq',
  'ZbZQ7Qf+J/Iw5XQomsyHqYo+/1NfBPAtJ7WNJEhvbAyZbA+LX8EDQdP3NGGAjNLR',
  'P/dczpy5wZJQ+3zxh8In3/irScx/1cB9kiXiHjCZ6er87iNpy2remvZf/Ho3713r',
  '/k504DKWX9fySpaloXnHH+wF4BGr0HCFOaIDQqP7RWSkGI2QDUzhkM0uhGO5g8Jn',
  'd61MT2l9rEZ4gDuWZ2KaEab8tezBGiv6tD6eNIKL/neSJKXI8MbJ8N94ctsQ4orW',
  'ajfuM9YUr172BXNM5soyj0yi7NSsIf7Huk5CAXwAF+dDJ2XDB/xzyiq9o6FOzmbU',
  '+4pM2k3vSAF+/8Y/W+4YZxFzJU+MmrkBDQRSkJRsAQgAxy35DBNeLd13F9+qp/2M',
  'wjkwDeSoCmfXNBZNlMJ1cSIsQvmO+UN6/4eXj3M10wA18pKf9azn+kU4RdtsWvZa',
  'FPICZDr0WKZzz7Bxa5izr3WKXEqXrFla3G3DZOanPD49R3pH6mnevecAt4vnSNiA',
  'rm2tUbTT+j2hxahVt5+g1xvdkOhL2FMpRGv/2IH6hvOnP6NFeSemO/5pNZpTGsGF',
  'v/JDP1pPItzepwe3TN/S8WekwSbwQyin0lOKkA9W0d08NAQqM0USF03AVndvaYHa',
  'vEQJ8qGm5nQjkyS0YBi9M0Hr3m/eHTTPYlj1xqXXHkvUy36wnykaRU4H7AQhVg3/',
  'qQARAQABiQEfBBgBAgAJBQJSkJRsAhsMAAoJEML4Ref2amW2/8sH/0swdfusCPEm',
  'VYJGrM3lxiDffyCzqqf6WySDCEyoKod863/0xVhY3BGSLUynwOX8bGm6M/JY5jjP',
  'DNsCaPsSkmE89VR7FxB2Eb6Ikk6M3CJcDA3HtyWO6zlTrKXenQU5AjF68izLUAYK',
  'R04QnQqHgsybENKMpMb7VNDLeYzcivab3Rtck1bDYLwDFqYfz+B7xzDqBHv2oCLB',
  'ChfY45HYSyT9+zhWuMVCB4icah6X2HRFKTBa0PTtG0rHhA7Pvzr8uHPuqmptnv7Z',
  '/E4nJglBsfzDMFGzlr+NFJijFgwzx6lqovnaMAan75BH6Y9obG7EkSpF9Ec9KKl4',
  'T2o9P7OT67k=',
  '=/Kyq',
  '-----END PGP PUBLIC KEY BLOCK-----'].join('\n');

function getKeyList() {
	const pubKeyData = [pub_key];
	return Promise.all(pubKeyData.map(key => openpgp.key.readArmored(key))).then(xs => xs.map(a => a.keys[0]));
}

query("#uploader").addEventListener('change', function(evt) {
	var files = evt.target.files; // FileList object
	var reader = new FileReader();
	reader.onload = (async function(evt) {
		var link;
		link = document.createElement('a');

		const keys = await getKeyList();

		var arrayBuffer = this.result;
		var fileData = new Uint8Array(arrayBuffer);
		const options = {
			message: openpgp.message.fromBinary(fileData),
			publicKeys: keys,
			privateKey: "",
			armor: true,
		};

		return openpgp.encrypt(options).then(results => {
			link.setAttribute('href', window.URL.createObjectURL(
			new Blob([results.data]), {type: "application/pgp-encrypted"})
			);
			link.setAttribute('download', "encrypted.file.gpg");
			link.innerHTML = files[0].name + ".pgp";
			query('#output').appendChild(link);
		});
	})();

	reader.readAsArrayBuffer(this.files[0]);

	var add = (function () {
	var counter = 0;
  return function () {counter += 1; return counter;}
 })();

  var file = document.getElementById("uploader");
  file.onchange = function(){
  if (file.files.length > 0){
		 document.getElementById('filename-1').innerHTML = file.files[0].name;
  }

  if (file.files.length > 1){
		document.getElementById('filename-1').innerHTML = file.files.length + " files selected";
	}
	}

	 if (file.files.length > 4){
		 alert("You can select up to 4 files\nPlease select again")
		 file.files.val = ""
		 document.getElementById('filename-1').innerHTML = "Choose a file ..."
   };

}, false);
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