Solution : https://service.sap.com/sap/support/notes/1324684 (SAP Service marketplace login required)
Key words : 
orasid> rman nocatalogrman> connect target /rman> configure encryption, oracle database option advanced security option, backupsto activate password-based encryption, oracle advanced security option, backup_dev_type = diskdisk_copy_cmd = rman_setand optional, archive log file backups, password-protected encrypted wallet, rman command configure, incremental database backups, lastthe password-based
Related Notes : 
       
| 1279682 | Support for Oracle data encryption in BR*Tools | 
| 974876 | Oracle Transparent Data Encryption (TDE) | 
| 828268 | Oracle Database 10g: New functions | 
| 740897 | Info about the Oracle license scope; Required Oracle options |