Amazon S3 provides authentication mechanisms to ensure that stored data is secured againstunauthorized access. Unless the customer who is uploading the data specifies otherwise, only thatcustomer can access the data. Amazon EMR customers can also choose to send data to Amazon S3using the HTTPS protocol for secure transmission. In addition, Amazon EMR always uses HTTPS tosend data between Amazon S3 and Amazon EC2. For added security, customers may encrypt theinput data before they upload it to Amazon S3 (using any common data compression tool); they thenneed to add a decryption step to the beginning of their cluster when Amazon EMR fetches the datafrom Amazon S3. Reference: https://aws.amazon.com/elasticmapreduce/faqs/