Encrypt a zip file with browserpgp javascript tool

Question

I would like to encrypt a zip file using OpenPGP.js (https://browserpgp.github.io/). All processing needs to be done on the client-side, without involvement of Node.js. Using the javascript-based browserpgp.js, encryption of plaintext file is easy, but encryption of zip files are challenging. I am attaching the code I use to encrypt the zip file. Since, the contents of zip file are not text, so I have used guides for working with binary data from https://github.com/openpgpjs/openpgpjs. I believe the resulting file after encryption of a zip file should be in raw/binary format, and the resulting file saved from the following encryption code is in binary. However, I verified it and its cannot be decrypted.

I am using the Kleopatra desktop OpenPGP tool (https://www.openpgp.org/software/kleopatra/) to verify if the resulting encrypted file. Using the tool, I tested to see if I can decrypt the encrypted file using my private key. The resulting binary file cannot be decrypted using the Kleopatra tool. So I was wondering what is wrong with this code, as the resulting file should be decryptable using Kleopatra.

You can create two public keys using the tool here: https://browserpgp.github.io

function openpgp_encryptZIPFile(){  
  var zip = new JSZip();
  zip.file("Hello.txt", "Hello World\n");
  var img = zip.folder("images");
  zip.generateAsync({type:"blob"})
  .then(function(content) {
      console.log('contents: ' + content);     
      encryptedZipFile = OpenPGPEncryptDataZipFile(content);
  });  
}

async function OpenPGPEncryptDataZipFile(zipBlob) 
{    
  //This is my public key
  const key1 = `somekey1`;  //you would have to put a public key here 
    //This is the testuser public key
  const key2 = `somekey2`; //you would have to put another public key here 
  const publicKeysArmored = [key1, key2];
  //create a combined key
  const publicKeys = await Promise.all(publicKeysArmored.map(armoredKey => openpgp.readKey({ armoredKey }))); 
    
  var binaryData = new Uint8Array(zipBlob);  
  
  //https://github.com/openpgpjs/openpgpjs/blob/main/README.md
  //For OpenPGP.js v4 syntax is:  const message = openpgp.Message.fromBinary(binaryData); 
  //For OpenPGP.js v5 syntax is:  const message2 = await openpgp.createMessage({ binary: binaryData });
  //`const {data: encrypted}' OR `const { message }' OR just `const encrypted'
  const  encrypted  = await openpgp.encrypt({
  message: await openpgp.createMessage({ binary: binaryData }),      
     encryptionKeys: publicKeys,
     //signingKeys: privateKey // optional
     format: 'binary'
  });
  console.log('encrypted: ' + encrypted);
  var encryptedBlob = new Blob([encrypted],{type: 'text/plain'});    
  //var encryptedBlob = new Blob([encrypted], {type: "octet/stream"});
  saveAs(encryptedBlob, 'test.zip.enc' ); 
}

Paul Butler · Accepted Answer · 2022-06-15 06:45:07Z

0

Someone from OpenPGPjs github repo answered this

new Uint8Array(zipBlob) most likely doesn't do what you think it does. Perhaps try new Uint8Array(await zipBlob.arrayBuffer()), or just ask JSZip for a Uint8Array instead of a Blob in the first place.

Also, octet/stream is not a valid MIME type. Perhaps you meant application/octet-stream?

So I changed new Uint8Array(zipBlob) to new Uint8Array(await zipBlob.arrayBuffer()) and it worked.

https://github.com/openpgpjs/openpgpjs/discussions/1535

answered Jun 15, 2022 at 6:45

Paul Butler

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