You have an application running on an EC2 Instance which will allow users to download flies from a private S3 bucket using a pre-signed URL. Before generating t...

You have an application running on an EC2 Instance which will allow users to download flies from a private S3 bucket using a pre-signed URL. Before generating the URL the application should verify the existence of the file in S3.
How should the application use AWS credentials to access the S3 bucket securely?