Is the encryption of a db predictable?

Databases
#1

I am just wondering. What if…

  • I store data in SQLite DB that a user can select.
  • The user can choose if the DB is going to be encrypted.
  • The EncryptionKey is a static string of characters

Can one figure out the EncryptionKey by just saving two sets of identical data, where one set is encrypted, and the other one isn’t?

#2

that would be a plain text attack and sounds possible.

#3

If you use a secure hash on the password, the encryption key may be recoverable, but not the text used for the hash.

#4