@webbuf/acb3dh

Authenticated encryption with ECDH key exchange.

ACB3DH = AES + CBC + Blake3 MAC + Diffie-Hellman

Uses secp256k1 ECDH to derive a shared secret, then encrypts with ACB3.

Installation

npm install @webbuf/acb3dh

Usage

import { acb3dhEncrypt, acb3dhDecrypt } from "@webbuf/acb3dh";
import { publicKeyCreate } from "@webbuf/secp256k1";
import { WebBuf } from "@webbuf/webbuf";
import { FixedBuf } from "@webbuf/fixedbuf";

// Alice and Bob generate key pairs
const alicePrivKey = FixedBuf.fromRandom<32>(32);
const alicePubKey = publicKeyCreate(alicePrivKey);

const bobPrivKey = FixedBuf.fromRandom<32>(32);
const bobPubKey = publicKeyCreate(bobPrivKey);

// Alice encrypts a message to Bob
const plaintext = WebBuf.fromUtf8("Hello Bob!");
const ciphertext = acb3dhEncrypt(alicePrivKey, bobPubKey, plaintext);

// Bob decrypts the message from Alice
const decrypted = acb3dhDecrypt(bobPrivKey, alicePubKey, ciphertext);
console.log(decrypted.toUtf8()); // "Hello Bob!"

How It Works

1. Derives shared secret using ECDH: sharedSecret(privKey, pubKey)
2. Hashes the shared secret with BLAKE3 to get the encryption key
3. Encrypts/decrypts using ACB3 (AES-CBC + BLAKE3 MAC)

Both parties can derive the same shared secret:

• Alice: sharedSecret(alicePriv, bobPub)
• Bob: sharedSecret(bobPriv, alicePub)

API

| Function | Description | | ------------------------------------------------ | ----------------------------- | | acb3dhEncrypt(privKey, pubKey, plaintext, iv?) | Encrypt with ECDH-derived key | | acb3dhDecrypt(privKey, pubKey, ciphertext) | Decrypt with ECDH-derived key |

License

MIT