React Native Virgil Crypto

This README is for 0.5.x version of the library. Check the 0.4.x branch for 0.4.x docs.

React Native bridge for Virgil Security Crypto Library for iOS and Android.

This library is a replacement for virgil-crypto-javascript and should be used in React Native projects. The main difference is that in virgil-crypto-javascript library a class named VirgilCrypto is exported from the module that you need to create instances of, whereas this library exports an "instance" of that class ready to be used. Also, stream encryption is not available as there is no stream implementation in React Native. We're investigating the options to support file encryption though.

Install

First, install the package:

yarn add react-native-virgil-crypto

Second, pick your version of React Native and use the provided project as a reference for your own project:

• React Native 0.59.x
• React Native 0.60.x
• React Native 0.61.x
• React Native 0.62.x

Last, you need to get familiar with the usage examples below:

Generate a key pair

Generate a Private Key with the default algorithm (ED25519):

import { virgilCrypto } from 'react-native-virgil-crypto';

const keyPair = virgilCrypto.generateKeys();

Generate and verify a signature

Generate signature and sign data with a private key:

import { virgilCrypto } from 'react-native-virgil-crypto';

const signingKeypair = virgilCrypto.generateKeys();

// prepare a message
const messageToSign = 'Hello, Bob!';

// generate a signature
const signature = virgilCrypto.calculateSignature(messageToSign, signingKeypair.privateKey);
// signature is a NodeJS Buffer polyfill
console.log(signature.toString('base64'));

Verify a signature with a public key:

// verify a signature
const isVerified = virgilCrypto.verifySignature(messageToSign, signature, signingKeypair.publicKey);

Encrypt and decrypt data

Encrypt Data on a Public Key:

import { virgilCrypto } from 'react-native-virgil-crypto';

const encryptionKeypair = virgilCrypto.generateKeys();

// prepare a message
const messageToEncrypt = 'Hello, Bob!';

// encrypt the message
const encryptedData = virgilCrypto.encrypt(messageToEncrypt, encryptionKeypair.publicKey);
// encryptedData is a NodeJS Buffer polyfill
console.log(encryptedData.toString('base64'));

Decrypt the encrypted data with a Private Key:

// decrypt the encrypted data using a private key
const decryptedData = virgilCrypto.decrypt(encryptedData, encryptionKeypair.privateKey);

// convert Buffer to string
const decryptedMessage = decryptedData.toString('utf8');

File encryption

To encrypt a file you will need to know its location in the file system. For images you can use React Native API, or a library such as react-native-image-picker or react-native-camera-roll-picker.

import { virgilCrypto } from 'react-native-virgil-crypto';

const keypair = virgilCrypto.generateKeys();

// this must be defined in your code
pickAnImage()
.then(image => {
  return virgilCrypto.encryptFile({
    // assuming `image` has a `uri` property that points to its location in file system
    inputPath: image.uri,
    // This can be a custom path that your application can write to
    // e.g. RNFetchBlob.fs.dirs.DocumentDir + '/encrypted_uploads/' + image.fileName,
    // If not specified, a temporary file will be created.
    outputPath: undefined,
    publicKeys: keypair.publicKey
  })
  .then(encryptedFilePath => {
    // encryptedFilePath is the location of the encrypted file in the file system
    // the original image file remain intact
    // you can now upload this file using `fetch` and `FormData`, e.g.:
    const data = new FormData();
    data.append('photo', {
      uri: 'file://' + encryptedFilePath,
      type: image.type,
      name: image.fileName
    });

    return fetch(url, { method: 'POST', body: data });
  });
});

Decryption works similarly to encryption - you provide a path to the encrypted file in the file system (network urls are not supported). You can use a library such as rn-fetch-blob or react-native-fs to download a file directly into file system.

import { virgilCrypto } from 'react-native-virgil-crypto';

const keypair = virgilCrypto.generateKeys();

// this must be defined in your code
downloadImage()
.then(downloadedFilePath => {
  return virgilCrypto.decryptFile({
    inputPath: downloadedFilePath,
    // This can be a custom path that your application can write to
    // e.g. RNFetchBlob.fs.dirs.DocumentDir + '/decrypted_downloads/' + image.id + '.jpg';
    // If not specified, a temporary file will be created
    outputPath: undefined,
    privateKey: keypair.privateKey
  })
  .then(decryptedFilePath => {
    return <Image src={`file://${decryptedFilePath}`} />
  });
});

It is also possible to calculate the digital signature of a file

import { virgilCrypto } from 'react-native-virgil-crypto';

const keypair = virgilCrypto.generateKeys();
// this must be defined in your code
pickAnImage()
.then(image => {
  return virgilCrypto.generateFileSignature({
    inputPath: image.uri,
    privateKey: keypair.privateKey
  })
  .then(signature => ({ ...image, signature: signature.toString('base64') }));
});

And verify the signature of a file

import { virgilCrypto } from 'react-native-virgil-crypto';

const keypair = virgilCrypto.generateKeys();

// this must be defined in your code
downloadImage()
.then(downloadedFilePath => {
  return virgilCrypto.verifyFileSignature({
    inputPath: image.downloadedFilePath,
    signature: image.signature,
    publicKey: keypair.publicKey
  })
  .then(isSigantureVerified => ({ ...image, isSigantureVerified }));
});

See the demo project for a complete example of working with encrypted files.

Group encryption

This library only provides crypto primitives to implement group chats.

First, you need to create a group session:

import { virgilCrypto } from 'react-native-virgil-crypto';

const keypair = virgilCrypto.generateKeys();

const groupSession = virgilCrypto.generateGroupSession('unique_identifier_of_the_group');

Then, you need to share this group session with users who you want to communicate with. Note that secure sharing of group sessions is not a responsibility of this library and is left for the developer to implement. It is provided out-of-the box in E3kit, though.

// exportedSession will be an array of Buffers that this exact session can be reconstructed from
const exportedSession = groupSession.export();

// now we serialize it to send to other group members
const serializedSession = exportedSession.map(m => m.toString('base64'));

// this must be implemented by the developer
shareGroupSession(groupSession.getSessionId(), serializedSession, groupMembers);

Upon receiving a shared group session, you will need to import its serialized representation:

import { virgilCrypto } from 'react-native-virgil-crypto';

function onSharedGroupSessionReceived(sharedGroupSession) {
  const sharedGroupSession = virgilCrypto.importGroupSession(sharedGroupSession);

  // you can now use sharedGroupSession to encrypt and decrypt messages
}

Encryption and decryption is as easy as calling encrypt and decrypt methods on the group session. When encrypting, you will need to provide the current user's private key to authenticate the encrypted message:

const message = 'Hello there! This is the beginning of our group chat.';

const encryped = groupSession.encrypt(message, myPrivateKey);

When decrypting, the public key of the sender must be provided to verify the authenticity of the message:

const decrypted = groupSession.decrypt(encrypted, senderPublicKey);

console.log(decrypted.toString('utf8'));

If you need to add new members to the group, you just share the current group session with them securely. If you need to remove someone from the group, you need to add a new epoch to the group - this produces what's called an epoch message - then share that epoch message with every group member except the ones you want to remove:

groupSession.addNewEpoch();

// now we serialize it to send to other group members
const serializedSession = groupSession.export().map(m => m.toString('base64'));

// this must be implemented by the developer
shareGroupSession(groupSession.getSessionId(), serializedSession, groupMembers);

Since this is pretty low-level we do not recommend using it directly. Instead, make sure to check out the higher-level API for group chats provided by E3kit.

Working with binary data

All of the methods of virgilCrypto object that accept binary data, accept them in the form of string or Buffer. All of the methods that return binary data, return them in the form of Buffer. We use this library as the native implementation is not available in react native. We re-export the Buffer from the module for your convenience:

import { Buffer } from 'react-native-virgil-crypto';

console.log(Buffer.from('hello Buffer').toString('base64')); // prints aGVsbG8gQnVmZmVy

Performance

See the sample project for a complete example that you can use to measure performance of this library on your own devices.

License

This library is released under the 3-clause BSD License.

Support

Our developer support team is here to help you.

You can find us on Twitter or send us email support@VirgilSecurity.com.

Also, get extra help from our support team on Slack.