Amazon S3 Webservice - Create Public Webspace

[KIM-KeepInMind]

Hello! I like to create a public webspace service with the Amazon S3 service in the background. Problem: I like to set up the service in that way, that the user (surfer/customer) uploads and downloads directly to/from Amazon S3. I don't like to buffer files on my server in a queue to upload them later on Amazon S3 for security and traffic reason. But if I will do it directly the anonymous user will have to send MY password and MY username in the HTTP POST (upload) to Amazon to get access. Big security Problem :eek: Is there any way to avoid this in some way?
THANKS a lot!