Give every symbol a code from 000 to 999. Write down the information in this form. Then the Key(Master) trick up our sleeve: Put a decimal point before it. Reduce the fraction to the simplest form. Then take a 6-inch platinum-iridium alloy bar and mark a line to split it into the fraction(using supercomputers, lasers, etc.). Store this Bar safely. Away from moisture, dust, etc.

In this way we can store any amount of information on a 6-inch bar, unlike CD's which have a limit. Or can we? Find the theoretical limitation of this method.