@transcend-io/penumbra

Penumbra

Fetch and decrypt files in the browser using whatwg streams and web workers.

Quickly and efficiently decrypt remote resources in the browser. Display the files in the DOM, or download them with conflux.

• Compatibility
• Usage
  • Importing Penumbra
    • With Yarn/NPM
    • Vanilla JS
  • .get
  • .encrypt
  • .getDecryptionInfo
  • .decrypt
  • .save
  • .getBlob
  • .getTextOrURI
  • .zip
  • .setWorkerLocation
• Examples
  • Display encrypted text
  • Display encrypted image
  • Download an encrypted file
  • Download many encrypted files
• Advanced
  • Prepare connections for file downloads in advance
  • Encryption Completion Event Emitter
  • Progress Event Emitter
  • Configure worker location
  • Waiting for the penumbra-ready event
• Contributing
• License

Compatibility

	.decrypt	.encrypt
Chrome	yes	yes
Safari	yes	no
Edge	yes	yes
Firefox	yes	yes

Usage

Importing Penumbra

With Yarn/NPM

yarn add @transcend-io/penumbra

# or
npm install --save @transcend-io/penumbra

import { penumbra } from '@transcend-io/penumbra';

penumbra.get(...files).then(penumbra.save);

Vanilla JS

<script src="lib/penumbra.js"></script>
<script>
  penumbra
    .get(...files)
    .then(penumbra.getTextOrURI)
    .then(displayInDOM);
</script>

Check out this guide for asynchronous loading.

.get

Fetch and decrypt remote files.

penumbra.get(...resources: RemoteResource[]): Promise<PenumbraFile[]>

.encrypt

Encrypt files.

penumbra.encrypt(options: PenumbraEncryptionOptions, ...files: PenumbraFile[]): Promise<PenumbraEncryptedFile[]>

size = 4096 * 128;
addEventListener('penumbra-progress', (e) => console.log(e.type, e.detail));
addEventListener('penumbra-encryption-complete', (e) =>
  console.log(e.type, e.detail),
);
file = penumbra.encrypt(null, { stream: new Uint8Array(size), size });
data = [];
file.then(async ([encrypted]) => {
  console.log('encryption complete');
  data.push(new Uint8Array(await new Response(encrypted.stream).arrayBuffer()));
});

.getDecryptionInfo

Get decryption info for a file, including the iv, authTag, and key. This may only be called on files that have finished being encrypted.

penumbra.getDecryptionInfo(file: PenumbraFile): Promise<PenumbraDecryptionInfo>

.decrypt

Decrypt files.

penumbra.decrypt(options: PenumbraDecryptionInfo, ...files: PenumbraEncryptedFile[]): Promise<PenumbraFile[]>

const { intoStream } = self;
const te = new TextEncoder();
const td = new TextDecoder();
const data = te.encode('test');
const { byteLength: size } = data;
const [encrypted] = await penumbra.encrypt(null, {
  stream: intoStream(data),
  size,
});
const options = await penumbra.getDecryptionInfo(encrypted);
const [decrypted] = await penumbra.decrypt(options, encrypted);
const decryptedData = await new Response(decrypted.stream).arrayBuffer();
return td.decode(decryptedData) === 'test';

.save

Save files retrieved by Penumbra. Downloads a .zip if there are multiple files.

penumbra.save(data: PenumbraFile[], fileName?: string): Promise<void>

.getBlob

Load files retrieved by Penumbra into memory as a Blob.

penumbra.getBlob(data: PenumbraFile[] | PenumbraFile | ReadableStream, type?: string): Promise<Blob>

.getTextOrURI

Get file text (if content is text) or URI (if content is not viewable).

penumbra.getTextOrURI(data: PenumbraFile[]): Promise<{ type: 'text'|'uri', data: string, mimetype: string }[]>

.zip

Zip files retrieved by Penumbra.

penumbra.zip(data: PenumbraFile[] | PenumbraFile, compressionLevel?: number): Promise<ReadableStream>

.setWorkerLocation

Configure the location of Penumbra's worker threads.

penumbra.setWorkerLocation(location: WorkerLocationOptions | string): Promise<void>

Examples

Display encrypted text

const decryptedText = await penumbra
  .get({
    url: 'https://s3-us-west-2.amazonaws.com/bencmbrook/NYT.txt.enc',
    mimetype: 'text/plain',
    filePrefix: 'NYT',
    decryptionOptions: {
      key: 'vScyqmJKqGl73mJkuwm/zPBQk0wct9eQ5wPE8laGcWM=',
      iv: '6lNU+2vxJw6SFgse',
      authTag: 'gadZhS1QozjEmfmHLblzbg==',
    },
  })
  .then((file) => penumbra.getTextOrURI(file)[0])
  .then(({ data }) => {
    document.getElementById('my-paragraph').innerText = data;
  });

Display encrypted image

const imageSrc = await penumbra
  .get({
    url: 'https://s3-us-west-2.amazonaws.com/bencmbrook/tortoise.jpg.enc',
    filePrefix: 'tortoise',
    mimetype: 'image/jpeg',
    decryptionOptions: {
      key: 'vScyqmJKqGl73mJkuwm/zPBQk0wct9eQ5wPE8laGcWM=',
      iv: '6lNU+2vxJw6SFgse',
      authTag: 'ELry8dZ3djg8BRB+7TyXZA==',
    },
  })
  .then((file) => penumbra.getTextOrURI(file)[0])
  .then(({ data }) => {
    document.getElementById('my-img').src = data;
  });

Download an encrypted file

penumbra
  .get({
    url: 'https://s3-us-west-2.amazonaws.com/bencmbrook/africa.topo.json.enc',
    filePrefix: 'africa',
    mimetype: 'image/jpeg',
    decryptionOptions: {
      key: 'vScyqmJKqGl73mJkuwm/zPBQk0wct9eQ5wPE8laGcWM=',
      iv: '6lNU+2vxJw6SFgse',
      authTag: 'ELry8dZ3djg8BRB+7TyXZA==',
    },
  })
  .then((file) => penumbra.save(file));

// saves africa.jpg file to disk

Download many encrypted files

penumbra
  .get([
    {
      url: 'https://s3-us-west-2.amazonaws.com/bencmbrook/africa.topo.json.enc',
      filePrefix: 'africa',
      mimetype: 'image/jpeg',
      decryptionOptions: {
        key: 'vScyqmJKqGl73mJkuwm/zPBQk0wct9eQ5wPE8laGcWM=',
        iv: '6lNU+2vxJw6SFgse',
        authTag: 'ELry8dZ3djg8BRB+7TyXZA==',
      },
    },
    {
      url: 'https://s3-us-west-2.amazonaws.com/bencmbrook/NYT.txt.enc',
      mimetype: 'text/plain',
      filePrefix: 'NYT',
      decryptionOptions: {
        key: 'vScyqmJKqGl73mJkuwm/zPBQk0wct9eQ5wPE8laGcWM=',
        iv: '6lNU+2vxJw6SFgse',
        authTag: 'gadZhS1QozjEmfmHLblzbg==',
      },
    },
    {
      url: 'https://s3-us-west-2.amazonaws.com/bencmbrook/tortoise.jpg', // this is not encrypted
      filePrefix: 'tortoise',
      mimetype: 'image/jpeg',
    },
  ])
  .then((files) => penumbra.save({ data: files, fileName: 'example' }));

// saves example.zip file to disk

Advanced

Prepare connections for file downloads in advance

// Resources to load
const resources = [
  {
    url: 'https://s3-us-west-2.amazonaws.com/bencmbrook/NYT.txt.enc',
    filePrefix: 'NYT',
    mimetype: 'text/plain',
    decryptionOptions: {
      key: 'vScyqmJKqGl73mJkuwm/zPBQk0wct9eQ5wPE8laGcWM=',
      iv: '6lNU+2vxJw6SFgse',
      authTag: 'gadZhS1QozjEmfmHLblzbg==',
    },
  },
  {
    url: 'https://s3-us-west-2.amazonaws.com/bencmbrook/tortoise.jpg.enc',
    filePrefix: 'tortoise',
    mimetype: 'image/jpeg',
    decryptionOptions: {
      key: 'vScyqmJKqGl73mJkuwm/zPBQk0wct9eQ5wPE8laGcWM=',
      iv: '6lNU+2vxJw6SFgse',
      authTag: 'ELry8dZ3djg8BRB+7TyXZA==',
    },
  },
];

// preconnect to the origins
penumbra.preconnect(...resources);

// or preload all of the URLS
penumbra.preload(...resources);

Encryption Completion Event Emitter

You can listen to download progress events by listening to the penumbra-encryption-complete event.

window.addEventListener(
  'penumbra-encryption-complete',
  ({ detail: { id, decryptionInfo } }) => {
    console.log(
      `finished encryption job #${id}%. decryption options:`,
      decryptionInfo,
    );
  },
);

Progress Event Emitter

You can listen to download and encryption progress events by listening to the penumbra-progress event.

window.addEventListener(
  'penumbra-progress',
  ({ detail: { percent, id, type } }) => {
    console.log(`${type}% ${percent}% done for ${id}`);
    // example output: decrypt 33% done for https://example.com/encrypted-data
  },
);

Note: this feature requires the Content-Length response header to be exposed. This works by adding Access-Control-Expose-Headers: Content-Length to the response header (read more here and here)

On Amazon S3, this means adding the following line to your bucket policy, inside the <CORSRule> block:

<ExposeHeader>Content-Length</ExposeHeader>

Configure worker location

// Set only the base URL by passing a string
penumbra.setWorkerLocation('/penumbra-workers/');

// Set all worker URLs by passing a WorkerLocation object
penumbra.setWorkerLocation({
  base: '/penumbra-workers/',
  decrypt: 'decrypt.js'
  zip: 'zip-debug.js' // e.g. manually use a debug worker
  StreamSaver: 'StreamSaver.js'
});

// Set a single worker's location
penumbra.setWorkerLocation({decrypt: 'penumbra.decrypt.js'});

Waiting for the penumbra-ready event

<script src="lib/penumbra.js" async defer></script>

const onReady = async ({ detail: { penumbra } } = { detail: self }) => {
  await penumbra.get(...files).then(penumbra.save);
};

if (!self.penumbra) {
  self.addEventListener('penumbra-ready', onReady);
} else {
  onReady();
}

Contributing

# setup
yarn
yarn build

# run tests
yarn test:local

# run tests in the browser console
yarn test:interactive

License