Design of a synchronized clock


I was living in a country where Internet wasn’t that fast so the younger me had the following idea for compressing data

Let say 2 parties want to send data to each other, we know that data can be represented by a number literally any data no matter the size can be just a giant number.

So let say the 2 parties have this perfect synchronized clock and a very fast one, I mean a clock that can count billions of billions ( equivalent of gbits of data ) in a short amount of time.

So for party 1 to send data to party 2 it only need to send 2 messages : start counting and stop counting.

So any data can be sent using only 2 bits lol.

How hard is it to design that clock ?