Encryption

decode.ts

// objectKey, encrypted

const decryptKey = await crypto.subtle.importKey(
  "jwk",
  {
    k: objectKey,
    alg: "A128GCM",
    ext: true,
    key_ops: ["decrypt"],
    kty: "oct",
  },
  { name: "AES-GCM", length: 128 },
  false, // extractable
  ["decrypt"],
);

const decrypted = await crypto.subtle.decrypt(
  { name: "AES-GCM", iv: new Uint8Array(12) },
  decryptKey,
  encrypted,
);
const decoded = new TextDecoder().decode(new Uint8Array(decrypted));

console.log(decoded); // '{"foo":"bar"}'

encode.ts

const key = await crypto.subtle.generateKey(
  { name: "AES-GCM", length: 128 },
  true, // extractable
  ["encrypt", "decrypt"],
);

const content = {
  foo: "bar",
};

const encrypted = await crypto.subtle.encrypt(
  { name: "AES-GCM", iv: new Uint8Array(12) /* don't reuse key! */ },
  key,
  new TextEncoder().encode(JSON.stringify(content)),
);

const objectKey = (await crypto.subtle.exportKey("jwk", key)).k;

console.log({ objectKey, encrypted });