Efficiently encrypt/decrypt large file with cryptojs

Question

I want to encrypt large string (200 MB). The string come from dataUrl (base64) corresponding to file.

I'm doing my encryption in the browser.

My issue is that at the moment, i chunked string into small part into an array. Then i encrypt this chunks.

At the moment encrypting the string will full the memory. Here is how i'm doing it.

var encryptChunk = function(chunk, index){
  encryptedChunks.push( aesEncryptor.process( chunk ));
  sendUpdateMessage( "encryption", index+1, numberOfChunks );
}
chunkedString.forEach(encryptChunk);
encryptedChunks.push( aesEncryptor.finalize() );

I assume that, there should be a better way of doing this. But i can't find a memroy efficient way of doing this.

Answer 1

I am doing something similar to you. To directly answer your question of "is there a more memory efficient way?" .. well I use a web worker for processing progressive ciphering which seems to work.

  //pass in what you need here
  var worker = new Worker("path/to/worker.js");

  worker.postMessage({
                key: getKeyAndIvSomehow(),
                file: file,
                chunkSize: MY_CHUNK_SIZE
            });

  worker.addEventListener('message', function (e) {
               // create the blob from e.data.encrypted
            });

You will need to import the cryptoJS script into your worker: importScripts('cryptoJS.all.min.js')