Motivating Question

  • At home, my wife and I often use this recipe (RHS) to make hummus.
  • One day, my wife got a secret recipe for a new flavor called ’Ummus’. She wants me to try it tonight and needs me to prepare the ingredients in advance.
  • However, using any communication tool comes with security risks. So how can she safely pass this secret recipe to me?
  • Any solution? Think about it!

Our solution

Actually, this is how we store the recipe at home. First, we list all possible ingredients in a fixed order.

Our solution

Then, we fill in the required amounts in the corresponding cells. For example, the classic flavor requires these numbers.

Our solution

Using the same method, we can record the amounts for two other flavors as well.

Our solution

For the ingredients that are not needed, we simply fill in with 0.

Our solution

This way, as long as my wife gives me this sequence of numbers 1, 0, 3, 2, 1, 0, 1, 1/4, 0, 1, she can pass the ‘Hummus’ recipe to me and no one understands it.

Oh no, it looks like I’ve already leaked our secret recipe…