Sounds like the personnumer (person number) system in Sweden.

Which is quite scary when I first arrived in Sweden. It's a lot like MyKad - your DOB and then last 4 digits is random and supposed to be pin.

But the personnummer system is integrated into all systems everywhere, from government to private businesses.

Anything you sign up like open bank account, go dentist, or discount card also use the personnummer.

Same with any website you log in to, there is no user name just use the personnumer.

It is really convenient, but also quite scary. You go to any store, if you forget your member card just tell the cashier your personnumer they will give you the bonus points/discount.

it's a bit scary to imagine that all your personal information can so easily be accessible by anyone with just 4 numbers.

Well the number is issued by the department that handles taxes, called Skatteverket.
I'm not sure if there is a separate National Registration Dept.