Let's look at reception which help us to hide the cell content without sheet protection. Nevertheless, the value will be shown in the formula bar and the cell will take part in calculations.
But it's not banal assignement white color to the text. We'll go another way. Open «Cell formatting», and in the tab «Number» in the window «Number formats» choose «All formats». And in the graph «Type» enter three semicolons «;;;». Press «ОК» and cell text is hidden.
How to use given trick - you decide.