libsodium Sealed Box for TweetNaCl.js

This library implements sealed box for TweetNaCl.

From libsodium's documentation:

Sealed boxes are designed to anonymously send messages to a recipient given its public key.

Only the recipient can decrypt these messages, using its private key. While the recipient can verify the integrity of the message, it cannot verify the identity of the sender.

A message is encrypted using an ephemeral key pair, whose secret part is destroyed right after the encryption process.

Without knowing the secret key used for a given message, the sender cannot decrypt its own message later. And without additional data, a message cannot be correlated with the identity of its sender.

Usage

This module can be installed from npm:

npm install tweetnacl-sealedbox-js

For use in web browsers, use sealedbox.web.js.

Then you can use it as follow:

var tweetnacl = require('tweetnacl');
tweetnacl.sealedbox = require('tweetnacl-sealedbox-js');

// generate box key pair
var keyPair = tweetnacl.box.keyPair();

// encrypt the message
var sealed = tweetnacl.sealedbox.seal(buffer, keyPair.publicKey);
// sealed will have the size of buffer.length + tweetnacl.sealedbox.overheadLength

// decrypt the message
var result = tweetnacl.sealedbox.open(sealed, keyPair.publicKey, keyPair.secretKey);

The message buffer should be a Uint8Array or Node.js's Buffer. String encoding functions can be found in tweetnacl-util-js.

Note that sealedbox.open may return null if the sealed box is tampered.

This library should be interoperable with libsodium's implementation of sealed box (i.e. libsodium sealed box can be opened in this library and vice-versa).

Security

I'm not a security expert, so use this at your own risk.

This library does not zero out memory except for the ephemeral secret key. However, the JavaScript run time in use may not guaranteed that the memory is securely wiped.

License

This library is licensed under the MIT license.