Implementing Data Masking in Supabase is all about using policies to control who can see sensitive information. Let's break it down step by step:

First things first, you need to connect to your Supabase project. You can do this through the Supabase UI or by using the Supabase client library. Pretty straightforward, right?

Next, head over to the "Table Editor" section in the UI. From there, pick the table where you want to set up data masking. Just click on 'Table' from the menu on the left and choose your table. Easy peasy.

Now, on the table you selected, click on the 'Policies' tab at the top. This is where the magic happens. You can add new policies or tweak the existing ones for data masking.

To add a new policy, hit the 'New Policy' button. You'll need to give your policy a name and specify which operations (Select, Insert, Update, Delete) it will cover.

Next up, define the policy by entering the necessary SQL condition in the 'Check Expression' field. This expression should return true or false based on the conditions you set to allow or deny access.

For instance, a common expression might be auth.uid() = user_id. This ensures that only authenticated users can see their own data. Makes sense, right?

Once you've defined the policy, click on the 'Apply' button to save your changes. The policy will now be active and will enforce the mask on the specified data fields.

And that's it! You've successfully implemented data masking in Supabase. Just remember, you'll need a good grasp of SQL and authorization to pull this off smoothly.