diff --git a/www/common/common-util.js b/www/common/common-util.js
index 2542e0a22..f5ba9a61c 100644
--- a/www/common/common-util.js
+++ b/www/common/common-util.js
@@ -89,5 +89,15 @@ define([], function () {
         return Math.floor(bytes / 1024 * 100) / 100;
     };
 
+    Util.fetch = function (src, cb) {
+        var xhr = new XMLHttpRequest();
+        xhr.open("GET", src, true);
+        xhr.responseType = "arraybuffer";
+        xhr.onload = function () {
+            return void cb(void 0, new Uint8Array(xhr.response));
+        };
+        xhr.send(null);
+    };
+
     return Util;
 });
diff --git a/www/common/cryptpad-common.js b/www/common/cryptpad-common.js
index 0c777b9c8..a1daa8b17 100644
--- a/www/common/cryptpad-common.js
+++ b/www/common/cryptpad-common.js
@@ -71,6 +71,7 @@ define([
     common.fixFileName = Util.fixFileName;
     common.bytesToMegabytes = Util.bytesToMegabytes;
     common.bytesToKilobytes = Util.bytesToKilobytes;
+    common.fetch = Util.fetch;
 
     // import hash utilities for export
     var createRandomHash = common.createRandomHash = Hash.createRandomHash;
diff --git a/www/file/file-crypto.js b/www/file/file-crypto.js
index 608b3bb6e..35e2f8037 100644
--- a/www/file/file-crypto.js
+++ b/www/file/file-crypto.js
@@ -7,6 +7,18 @@ define([
     var plainChunkLength = 128 * 1024;
     var cypherChunkLength = 131088;
 
+    var encodePrefix = function (p) {
+        return [
+            65280, // 255 << 8
+            255,
+        ].map(function (n, i) {
+            return (p & n) >> ((1 - i) * 8);
+        });
+    };
+    var decodePrefix = function (A) {
+        return (A[0] << 8) | A[1];
+    };
+
     var slice = function (A) {
         return Array.prototype.slice.call(A);
     };
@@ -64,6 +76,7 @@ define([
         var nonce = createNonce();
         var i = 0;
 
+        decodePrefix([]); // TODO
         var takeChunk = function () {
             var start = i * cypherChunkLength;
             var end = start + cypherChunkLength;
@@ -126,6 +139,8 @@ define([
     var encrypt = function (u8, metadata, key) {
         var nonce = createNonce();
 
+        encodePrefix(); // TODO
+
         // encode metadata
         var metaBuffer = Array.prototype.slice
             .call(Nacl.util.decodeUTF8(JSON.stringify(metadata)));
diff --git a/www/file/main.js b/www/file/main.js
index a7a0f0fb2..223fcc41e 100644
--- a/www/file/main.js
+++ b/www/file/main.js
@@ -24,16 +24,6 @@ define([
 
     Cryptpad.addLoadingScreen();
 
-    var fetch = function (src, cb) {
-        var xhr = new XMLHttpRequest();
-        xhr.open("GET", src, true);
-        xhr.responseType = "arraybuffer";
-        xhr.onload = function () {
-            return void cb(void 0, new Uint8Array(xhr.response));
-        };
-        xhr.send(null);
-    };
-
     var myFile;
     var myDataType;
 
@@ -78,6 +68,7 @@ define([
                             var uri = ['', 'blob', id.slice(0,2), id].join('/');
                             console.log("encrypted blob is now available as %s", uri);
 
+                            // TODO use cryptpad-common utilities
                             window.location.hash = [
                                 '',
                                 2,
@@ -88,6 +79,7 @@ define([
 
                             $form.hide();
 
+                            // check if the uploaded file can be decrypted
                             var newU8 = FileCrypto.joinChunks(chunks);
                             FileCrypto.decrypt(newU8, key, function (e, res) {
                                 if (e) { return console.error(e); }
@@ -97,7 +89,7 @@ define([
 
                                 var defaultName = Cryptpad.getDefaultName(Cryptpad.parsePadUrl(window.location.href));
                                 APP.updateTitle(title || defaultName);
-
+                                Cryptpad.alert("successfully uploaded: " + title);
                             });
                         });
                     });
@@ -212,7 +204,7 @@ define([
 
         if (!uploadMode) {
             var src = Cryptpad.getBlobPathFromHex(hexFileName);
-            return fetch(src, function (e, u8) {
+            return Cryptpad.fetch(src, function (e, u8) {
                 // now decrypt the u8
                 if (e) { return window.alert('error'); }
                 var cryptKey = secret.keys && secret.keys.fileKeyStr;