Access via api S3 bucket private

im trying to find the best solution on a API that im developing, basically in my API i store images on s3 private buckets, and in the private buckets i need to be displayed on a mobile app.

I have 2 solutions but are not the best in my view:

1) Send the images in base64. Problem: Need to change the app to read the base64 images since before was reading by accessing a url.

2) Access the private bucket authenticating in app using s3 credentials Problem: Not completelly secure, exposing the credentials saving in the app.

Does someone cross by the same situation? Any idea.

via Chebli Mohamed