How to make database secure and inaccessible without an app?

Question

i want to encrypt all the data to be stored in the database using two keys. one with developer and one with client. any access to make database open shall allow only to see encrypted data

Answer 1

Step 1. Decide a strong encryption/decryption algorithm. Both encryption and decryption must operate with the same key.
Step 2. Create encryption procedures in PL/SQL to write/update data to a table.
Step 3. Create decryption procedures in PL/SQL to read data to a table.
Step 4. Now pass the data and encryption key to these procedures from your application or programming language.

Although in this approach, data is accessible by any means, still can only used by the same application(Obviously only if encryption key is stored safely).

You can also use different encryption keys for different tables.

Happy coding :)