Hi Charmonder,
I tried the [Amazon Simple Storage Service (S3)] component to upload and download a file to a bucket, with Server Side Encryption enabled, successfully.
What the component currently does not support is to specify a different key and encryption method other than the one configured as default for the s3 bucket.
Could it be that the account you're using doesn't have the necessary permissions to upload to that bucket? Have you managed to overcome the issue?