From Xojo Documentation
Specifies the encryption key used to open an encrypted database or to encrypt a database.
To encrypt a new database, specify this value before calling CreateDatabaseFile.
To connect to an encrypted database, specify this value before calling Connect.
To encrypt an existing database, use the Encrypt method after you have created or connected to the database.
To decrypt an existing database, use the Decrypt method after you have connected to the encrypted database.
AES-256 encryption is used starting with 2018r1. Before that, AES-128 encryption was used.