The application encrypts the data, you save in the database the data encrypted. When you retrieve the info, the app decrypt it.
This makes it impossible to support any analytical SQL queries against the DB. Look into how to enable encryption at rest on whichever DB you choose.
So put an SQLite database on a Luks-encrypted partition or a Luks-encrypted filesystem in a file.
Well, sqlite
For the low low price of $2000
Which is a rounding error in any commercial business.
SQLCipher fits that bill. I had some issues with language integration but depending on what you're using it might work for you.
Turso: https://docs.turso.tech/libsql#encryption-at-rest
Also, DuckDB devs said it was planned: https://github.com/duckdb/duckdb/discussions/4512
Depending on the application could you just mount a filesystem that supports encryption? Even if it’s just mounting a .tar file.
Firebird: 13.8. Database Encryption https://www.firebirdsql.org/file/documentation/chunk/en/refdocs/fblangref30/fblangref30-security-dbcrypt.html
Encryption is usually implemented in the server or client code. Why do you want the database to handle encryption?
It is for as desktop app that stores data on a user drive.
Then the application should encrypt the data saved to the db.
I can't think of any scenario where it would make sense for the db to handle encryption.
Encryping by the application would kill the use of a lot of sql features such as SUM.