Error in Uploading Private File

Not able to upload a private file into Amazon S3. with the following file system configuration:

Public file system path: s3://dh_public

Private file system path: s3://dh_private

Default download method: Amazon Simple Storage Service

Field upload destination: Private files.

Error: The file could not be uploaded (The file permissions could not be set on private://field/image)

Bucket has read and write permissions. After saving file config it automatically created folders dh_public and dh_private with proper ,htaccess file

If upload destination is Amazon S3 -- works fine but every one can see the file

Please let me know how to store private file in Amazon S3.

Thanks,
Ujwal P