@futuretense/ed25519-box

Simple public-key encryption for nodejs and browsers

Draws inspiration from box of NaCl, but works with ed25519 keys right away.

ed25519-box vs nacl-box

ed25519-box uses ed25519 key-pairs directly, whereas w/ nacl-box you have to transform ed25519 keys to curve25519 keys.
ed25519-box gives you the choice of not using authentication, whereas nacl-box always adds a Poly1305 authentication tag.
ed25519-box uses standard crypto APIs, already included in node.js, or in your browser -- no extra dependencies

Installation

npm install @futuretense/ed25519-box

Usage

import { encrypt, decrypt } from '@futuretense/ed25519-box';

Functions

Encrypt

async encrypt(privKey, pubKey, input, nonce, authenticate = true);

Parameter	Type	Description
privKey	Uint8Array	The private key of the sender
pubKey	Uint8Array	The public key of the recipient
input	Uint8Array	The data to be encrypted
nonce	Uint8Array	The message nonce
authenticate	Boolean	Should it be authenticated?

Return value	Description
Promise<Uint8Array>	The encrypted data

Decrypt

async decrypt(privKey, pubKey, input, nonce, authenticate = true);

Parameter	Type	Description
privKey	Uint8Array	The private key of the recipient
pubKey	Uint8Array	The public key of the sender
input	Uint8Array	The encrypted data
nonce	Uint8Array	The message nonce
authenticate	Boolean	Should it be authenticated?

Return value	Description
Promise<Uint8Array>	The decrypted data

Authentication

Authenticated mode (which is the default) uses AES-256-GCM to add integrity control to the pot, to make it possible to verify that the provided cipher output has been encrypted by someone with access to the encryption key.

Authentication adds sixteen bytes of data to the output.

Un-authenticated mode uses AES in counter mode (AES-256-CTR), and doesn't add any extra data.

Nonce

Authenticated mode has a twelve byte nonce, and un-authenticated mode has a sixteen byte nonce.

In both modes, the nonces provided are used as initial values for the counters.

Nonce re-use

The idea is that, for a given key, you should consider each counter value as "burnt" whenever you use it. -- Thomas Pornin

Both modes use stream ciphers that divide the input data into 128-bit blocks, which are then exclusive-or:ed with the result of a function based on the encryption key and the counter value for a block.

If a (key, counter)-combination is ever used twice, this can be exploited to arrive at a block that's the exclusive-or of the two unencrypted input blocks.