ELI5: MPC Encryption

Imagine you have a piggy bank where you keep all your money. You don’t want anyone else to see how much money you have, so you lock the piggy bank with a key. 

This lock is like encryption: it keeps your money safe so that only you, using your key, can see what’s inside.

Now, let’s say you and your friends all have piggy banks, and you want to figure out how much money everyone has together, but no one wants to reveal their amount. Usually, you’d have to unlock your piggy banks and show each other your money, but that would mean everyone sees how much you have.

This is where a specific type of encryption comes in, termed “Multi-Party Computation,” or MPC for short. MPC is not too challenging to understand, and we’ll simplify it below. 

At a high level, it provides a clever way to work together on figuring out the total amount of money without anyone having to open their piggy banks.

Why would you want this? 

In real life, there are many situations where people or companies need to work together without revealing their private information. Examples include:

• Voters want to trust the official vote outcome without having their individual votes known.
• Different banks want to make strategic decisions while keeping their client’s information private. For example, analyzing industry trends or improving fraud detection.
• Different companies have a lot of information that they can combine for better decision-making. For example, medical diagnosis would benefit immensely from this while wishing to keep that information private.

MPC enables a tremendous amount of use cases in a fast, secure, and cost-effective way that anyone can implement.

So, in a nutshell:

• Encryption is like locking your piggy bank so no one can see what’s inside.
• MPC is like working together with your friends to figure out how much money you all have without ever opening the piggy banks.
• Understanding how this example works means you can understand how MPC works when applied across many other use cases.

Now that you understand why encryption is necessary, let’s dive into how MPC works with our piggy bank example.

Piggy Banks: How MPC Works in Action

Let’s consider the piggy bank example: how could five people determine the total amount they all while keeping each person’s amount a secret?

Here’s how it would work:

• Add a Secret Number: Everyone forms a circle, picks a secret number, and adds it to their piggy bank amount. For example, if you have $10 in your piggy bank and you choose the secret number 7, tell the next person you have $17.
• Pass It On: The next person does this same, adds it to your number (17), and passes it on. If they have $20 and they choose the secret number 3, they would get $23. When they add the $17 from you to this, they arrive at $40 and they then tell the next person in line.
• Final Calculation: This continues until everyone in the group has contributed once, arriving at a total of everyone’s numbers mixed with all of the secret numbers. 

It is important to note that each participant chose a secret number for themself and that none of the chosen secret numbers are ever shared between the participants.

Here’s what this would look like:

The final is $93, but remember, no one knows how much anyone else has because all the numbers are scrambled with secret numbers.

The final step is to remove the secret numbers.

To figure out the real total, the MPC technology itself ensures that each person’s secret number is subtracted in a secure and private manner. This means that the final amount revealed is the combined amount of money in everyone’s piggy banks, while each individual amount remains private. No one can figure out anyone else’s secret number or the amount they have in their piggy bank.

Why It’s Cool:

• No one learns anyone else’s individual amount. All they see are scrambled numbers.
• You get the total amount without revealing your secrets!

MPC works similarly, but instead of piggy banks, it’s about protecting data. Multiple people (or computers) work together to solve a problem without anyone seeing the other’s private information. It's like magic, but it’s actually some really clever math!

Now, our example was simple and in reality:

• We might have more complex information
• We might have more users
• We might have people who lie
• We might need things to be fast (like, really fast)

However, the general concepts still apply.

And it’s worth noting that MPC is the best overall way of doing calculations on data that remains private. It’s fast, low-cost, and works for many different types of companies and use cases.

In fact, we covered the reasons why in-depth in our recent blog post. You can also check out our recent Whiteboard Session covering MPC for more details.

Start Building with MPC!

MPC is a game-changing technology that allows groups to work together without revealing their private data. Whether it’s banks sharing trends without exposing client details or companies working in tandem on a project, MPC can handle it all while keeping things private.

By keeping each individual’s information hidden and only revealing the final result, MPC is a powerful tool that ensures privacy and confidentiality, even when multiple parties are involved.

If you’d like to learn more about how to start building with MPC, reach out to us today!

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