You can encrypt access 2003 databases, though IIRC only with (at best) RC4 encryption. Since that is very easy to screw up you are somewhat dependant on MS having implemented it well.

Securing data-access pages: This applies to data that is accessed via a Web page. The Web pages are stored in the file system, so only file system security applies.

Encrypt and password-protect your database in Microsoft Access. Learn how to set a Password on an Access Database.

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