Oracle Advanced Security is an optional licenced Oracle 11g Database add-on.  Oracle Advanced Security Transparent Data Encryption (TDE) offers two different features:  column encryption and tablespace encryption.  TDE Tablespace Encryption 11.2.0.1 is now certified with Oracle E-Business Suite Release 11i.

What is Transparent Data Encryption (TDE) ?

Oracle Advanced Security Transparent Data Encryption (TDE) allows you to protect data at rest. TDE helps address privacy and PCI requirements by encrypting personally identifiable information (PII) such as Social Security numbers and credit card numbers.

TDE is completely transparent to existing applications with no triggers, views or other application changes required. Data is transparently encrypted when written to disk and transparently decrypted after an application user has successfully authenticated and passed all authorization checks. Authorization checks include verifying the user has the necessary select and update privileges on the application table and checking Database Vault, Label Security and Virtual Private Database enforcement policies.