React Native (Expo SDK 54): How to encrypt request body when sending FormData (file upload)?

I’m using React Native with Expo SDK 54, and I have an API client built with Axios.
All my normal JSON requests are encrypted before being sent to a .NET 6 backend. When I send a normal JSON body, my encryption works correctly, but when i use formData - it does not:

const client = axios.create({
  baseURL: apiUrl,
});

client.interceptors.request.use(async (config) => {
  // Add tokens

  config.data = await encrypt(config.data);

  if (config.data instanceof FormData) {
    return config;
  }

  if (config.data) {
    config.headers["Content-Type"] = "application/json";
  }

  return config;
});

const formData = new FormData();
formData.append("file", {
  uri: file.uri,
  name: "test.jpg",
  type: "image/jpeg",
});

**
How can I encrypt a request body that contains FormData (multipart/form-data) in React Native?**

Is it even possible to encrypt and then decrypt FormData, or do I need to use another approach?

Specifically:

• Should I encrypt only JSON metadata and send the file unencrypted?

• Should I avoid FormData entirely if encryption is required?

• Is there a correct way to encrypt multipart/form-data in React Native?