A wrapper service for SubtleCrypto Browser API

cryptography.service.ts

import TextManipulationHelper from './text-manipulation';

import type { CryptographyManager, EncryptionKeyManager, EncryptionPayload } from './cryptography.model';

class CryptographyService<T extends AesKeyGenParams | HmacKeyGenParams | Pbkdf2Params = AesKeyGenParams>
  implements EncryptionKeyManager, CryptographyManager
{
  public readonly algorithm: T;

  constructor(algo: T) {
    // See: https://developer.mozilla.org/en-US/docs/Web/Security/Secure_Contexts
    if (window.isSecureContext) this.algorithm = algo;
    else throw new Error('Impossible to use cryptography service due to non-secured context');
  }

  // IV: Initial Vector

  public generateIv = (): Uint8Array => window.crypto.getRandomValues(new Uint8Array(12));

  // Encryption Key

  private generateKey = async (): Promise<CryptoKey> =>
    window.crypto.subtle.generateKey(this.algorithm, true, ['encrypt', 'decrypt']);

  public parseKey = async (key: ArrayBuffer) =>
    window.crypto.subtle.importKey('raw', key, this.algorithm, true, ['encrypt', 'decrypt']);

  public readKey = async (key: CryptoKey): Promise<ArrayBuffer> => window.crypto.subtle.exportKey('raw', key);

  // Data encryption

  public encrypt = async (data: string): Promise<EncryptionPayload> => {
    const cryptoKey = await this.generateKey();
    const encoded = TextManipulationHelper.encode(data);

    const iv = this.generateIv();
    const algo = { ...this.algorithm, iv };

    const cipher = await window.crypto.subtle.encrypt(algo, cryptoKey, encoded);

    const key = await this.readKey(cryptoKey);
    return { key, cipher, iv };
  }

  // Data decryption

  public decrypt = async (cipher: ArrayBuffer, key: CryptoKey, iv: Uint8Array): Promise<string> => {
    const algo = { ...this.algorithm, iv };
    const encoded: ArrayBuffer = await window.crypto.subtle.decrypt(algo, key, cipher);

    return TextManipulationHelper.decode(encoded);
  }
}

const AES_CGM_ALGORITHM: AesKeyGenParams = { name: 'AES-GCM', length: 256 };

export default new CryptographyService(AES_CGM_ALGORITHM);