that's the right way to protect your ISP

I presume you mean "IP" there - Intellectual Property?

If your IP needs such protection, why are you delivering the source at all?
Why not just deliver a library, or something?

If you are a Contractor, this should be negotiated in the Contract details - whether you are providing Binary only, or full source.
If the Contract deliverables specify full source, you could be considered in breach if it's deliberately obfuscated, as you seem to be suggesting.

If you are an Employee, your contract of employment should have something to say about ownership of IP created in the course of that employment.