Oracle 11g encrypt traffic from clients to database server
Check the licensing again, these options became free about 2 years ago.

http://docs.oracle.com/cd/E11882_01/license.112/e47877/options.htm#DBLIC143


  Network encryption (native network encryption and SSL/TLS) and strong
  authentication services (Kerberos, PKI, and RADIUS) are no longer
  part of Oracle Advanced Security and are available in all licensed
  editions of all supported releases of the Oracle database.