System package SYS.DBMS_CRYPTO

Implement a subset of the system package SYS.DBMS_CRYPTO:

• Constant DBMS_CRYPTO.ENCRYPT_AES256 - algorithm
• Constant DBMS_CRYPTO.CHAIN_CBC - Block Cipher Chaining Modifier
• Constant DBMS_CRYPTO.PAD_PKCS5 - Block Cipher Padding Modifier
• Function DBMS_CRYPTO.ENCRYPT
• Procedures DBMS_CRYPTO.ENCRYPT - overloaded
• Function DBMS_CRYPTO.DECRYPT()
• Procedures DBMS_CRYPTO.DECRYPT - overloaded