Which DB should be used for securiy purpose and fast

Question

Hello members I have to build a project on Astrology and for that purpose which database is best suited for faster retrieval of data and it ahould be secured. Secured in the sense means no one can access/open that database unless provided the username and password (i.e from connection string) and also don't want to encrypt the columns that's slow down the performance. This application should be offline and might be online in future. I have already used Sql server express in past projects but it is having slow performance. Application to be used :wpf Please sugest what db should be used to the optimal performance. Thanka Devendra