How to tighten encryption on S3 using a client key in python?

Question

Python

I have a test case of uploading and downloading a file: pastebin.com/wXNnYtm1
Based on the documentation, I added headers with the key, its md5, and the algorithm:

header = {
            "x-amz-server-side-encryption-customer-algorithm" :
             "AES256",
            "x-amz-server-side-encryption-customer-key" :
             "MAAxAHQAZQBzAHQASwBlAHkAVABvAFMAUwBFAEMAIQA=",
            "x-amz-server-side-encryption-customer-key-MD5" :
             "fUgCZDDh6bfEMuP2bN38mg=="
}

As a result, I get the answer:

reply: 'HTTP/1.1 403 Forbidden\r\n'

But if you remove the headers from both requests, then the file goes back and forth. Can anyone help me figure out what's wrong with me?