aes-universal-web

Web implementation of aes-universal for Expo applications.

Installation

npm install aes-universal-web

Peer Dependencies

This package requires the following peer dependencies:

• aes-universal: The base package that defines the interfaces
• u8a-utils: Utility functions for Uint8Array operations

npm install aes-universal u8a-utils

Usage

WebAesCipher provides AES encryption and decryption using Web Crypto API, supporting both CBC and GCM modes.

CBC Mode

CBC mode supports the following encryption algorithms:

• A128CBC-HS256: 32 bytes CEK (16 bytes for encryption + 16 bytes for MAC)
• A192CBC-HS384: 48 bytes CEK (24 bytes for encryption + 24 bytes for MAC)
• A256CBC-HS512: 64 bytes CEK (32 bytes for encryption + 32 bytes for MAC)

In CBC mode, the Content Encryption Key (CEK) includes both the encryption key and the MAC key.

GCM Mode

GCM mode supports the following encryption algorithms:

• A128GCM: 16 bytes CEK
• A192GCM: 24 bytes CEK
• A256GCM: 32 bytes CEK

In GCM mode, the Content Encryption Key (CEK) is used directly for encryption.

Example: AES-128

CBC Mode (A128CBC-HS256)

import { webAesCipher } from 'aes-universal-web';

const randomBytes = (size: number): Uint8Array => {
  const bytes = new Uint8Array(size);
  crypto.getRandomValues(bytes);
  return bytes;
};

const enc = 'A128CBC-HS256';
const plaintext = new Uint8Array([1, 2, 3, 4]);
const aad = new Uint8Array([5, 6, 7, 8]);

// Generate CEK and IV
const cek = randomBytes(webAesCipher.getCekByteLength(enc));
const iv = randomBytes(webAesCipher.getIvByteLength(enc));

// Encrypt data
const { ciphertext, tag } = await webAesCipher.encrypt({
  enc, // AES-128 in CBC mode with HMAC-SHA-256
  cek,
  plaintext,
  aad, // Must use the same AAD for decryption
  iv,
});

// Decrypt data
const decrypted = await webAesCipher.decrypt({
  enc,
  cek,
  ciphertext,
  tag,
  iv,
  aad, // Must use the same AAD as encryption
});

expect(decrypted).toEqual(plaintext);

GCM Mode (A128GCM)

import { webAesCipher } from 'aes-universal-web';

const randomBytes = (size: number): Uint8Array => {
  const bytes = new Uint8Array(size);
  crypto.getRandomValues(bytes);
  return bytes;
};

const enc = 'A128GCM';
const plaintext = new Uint8Array([1, 2, 3, 4]);
const aad = new Uint8Array([5, 6, 7, 8]);

// Generate CEK and IV
const cek = randomBytes(webAesCipher.getCekByteLength(enc));
const iv = randomBytes(webAesCipher.getIvByteLength(enc));

// Encrypt data
const { ciphertext, tag } = await webAesCipher.encrypt({
  enc, // AES-128 in GCM mode
  cek,
  plaintext,
  aad, // Must use the same AAD for decryption
  iv,
});

// Decrypt data
const decrypted = await webAesCipher.decrypt({
  enc,
  cek,
  ciphertext,
  tag,
  iv,
  aad, // Must use the same AAD as encryption
});

expect(decrypted).toEqual(plaintext);

Development

Setup

1. Clone the repository
2. Install dependencies:

   npm install

Scripts

• npm run build - Build the library
• npm test - Run tests

License

MIT