To ensure that your data is properly secured, Oracle recommends that you make RMAN backup encryption a standard part of your backup processes. This recommendation is even more important to implement when you are storing critical backup data off-premises. Encrypting RMAN backups on Amazon S3 can also assist you in meeting key audit and regulatory compliance requirements for your organization's data.
See Also:
Encryption of Backup Sets for a discussion of RMAN encryption options.