Putting the Crypto in Cryptocurrency: a Guide for Secure Multi-Party Computation on the Blockchain

By Stan Peterson
December 6, 2021 Updated December 6, 2021
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Security concept: blue opened padlock on digital background, 3d render

As the human race has continued to evolve their technology, there have been near constant innovations in how to develop knowledge.  Ironically, for each new innovation for developing this knowledge, there have been two others created in parallel:  how to steal this knowledge, and how to protect it.  

Fast forward to our current world, and the only real change is the speed of that innovation.  We are finding more and more treasure troves of knowledge and insight, along with the need to communicate this to trusted partners.  However, there are many parties who are very motivated to steal this information, be it personal data, company secrets, or digital assets.  Thankfully, there have been two key technologies working in parallel to keep information safe:  Multi-Party Computation (MPC) and Blockchain.  

Blockchain has become a common phrase, with more and more people at least understanding the basics.  While the technology is over a decade old, the biggest mainstream-driving phase has been in the last few years.  MPC on the other hand has been in development since the 1980’s, and has grown steadily since.  On the surface, the two technologies have similar aims: to simultaneously share and protect information without a trusted third party.   How each technology accomplishes this is different however, and blockchain has shown that there are vulnerabilities in crucial areas.  It has only been recently that the two technologies have been paired to create a “best of both worlds”, with very few teams with the technical knowledge to master both sides.  Partisia Blockchain is one such example.  Instead of joining the wave of blockchain projects and deciding to also implement MPC, they have been active first as an MPC provider for years, and have paired blockchain technology with the veteran Partisia MPC applications.  

But what exactly is MPC, why does blockchain need additional protection from attacks, and what applications are just begging for the MPC/blockchain partnership?

MPC Basics: What You Need to Know

Blochain information encryption. Cyber security, crypto currency.

The most important thing to realize about MPC is, unfortunately, it is incredibly complex.  One could focus their entire PhD study on a small aspect of MPC.  The good news is, the problem that kicked off the entire industry is easier to grasp.  It’s called “Yao’s Millionaire Problem”, which is summarized like this:  Two employees, Alice and Bob, want to know if they are being paid the same amount.  They don’t want to share their salary, nor do they trust any person or computer with their private salary information.  The problem is, how do they answer the question (are they being paid the same) without giving up private information?  There are actually a number of answers to this, but the initial answer was to get a number of lockable suggestion boxes (locked, but has a slot to insert a slip of paper).  These boxes represent different salaries.  Bob takes the key to the box representing his salary and destroys the other keys.  Alice takes slips of paper, writes a “yes” on one and puts it into the box representing her salary, and writes a “no” on the others before inserting them into the remaining boxes.  Bob then privately opens the box representing his salary, then shows the paper to himself and Alice to answer their question.  Amazing, right?

Now consider this on a grand scale.  MPC can compute a very large range of public problems, using inputs from individuals that do not share their private information but nevertheless contribute to solving computation problems that use the information of each contributor.  This allows for progress to be made without sacrificing private information, without having private information together in one place (this information is distributed across parties without the ability to steal information if one input is compromised), and without the need for a third party.  

Blockchain Shortfalls:  Cracks in the Armour

At first glance, blockchain shares some of the key features of MPC.  Using the hash, parties can verify truth without knowing private information.  This is great with information on-chain, but the weaknesses of blockchain lie in that moment when transactions are made.  Let’s look specifically at the problem of digital currency, though the problem extends well beyond that (digital assets, private information, etc.).  Say you have digital currency.  Now what?  Well, if you want to protect it, a great solution is to use cold storage or a hardware wallet.  With either, the currency is stored offline, and in the case of the hardware wallet, is treated the way a wallet full of cash is:  Very secure from online theft, though theft or loss can happen offline as well.  What happens though if you actually want to spend that currency?  For cold/hardware solutions, it means a tedious process to get the currency available to access and use.  At this point the currency is attached to some network in order to transfer it.  This point in time is extremely vulnerable, and many people have lost millions (or more) by their currency stolen through a compromised key, a spoofed target address, or other ways.  With all of blockchain’s secure features, this area has cost victims a great deal of money.

MPC on the Blockchain: Three Breakthrough Applications

With MPC on the blockchain, there is good news for anyone who likes to avoid having their money or information stolen.  With MPC applied in those few areas where blockchain is vulnerable, the system as a whole becomes significantly more robust and secure—without losing speed, economy, or scalability.

The first application is protecting secret keys.  Simply put, it is nearly impossible to steal someone’s key if it is widely distributed among many devices, and each device can deliver its portion without 1) compromising their information/location, and 2) the parts of the key never have to combine into one vulnerable place.  The second application is preserving the privacy of smart contracts.  The easiest example is an auction, where buyers want the benefits of a smart contract showing their bid and transfer of ownership, but without that contract being public knowledge.  MPC is able to keep key information secret while at the same time verifying all the key elements of a smart contract.  Third, there are many areas where only some parts of a blockchain benefit from MPC, and the nature of MPC allows its use to be selective as a team develops their protocol.  The applications for targeted use of MPC on a blockchain are endless by empowering specific components with MPC, ensuring an application that is still efficient, effective, and as lightweight as possible.

Wrapping Up

MPC is only just beginning its run on blockchain.  Though it can’t go back in time to prevent the blockchain hacks/thefts that have occurred, it can go a very long way to ensuring those types of hacks don’t—and can’t—happen.  This is great news as the industry is struggling more and more with ways to benefit from blockchain security without destroying any usefulness by having unscalable solutions (yes, we’re talking about Ethereum).  2022 will be an exciting year as we see MPC go mainstream on the blockchain with Partisia’s platform (and perhaps others), providing that protection we’ve always needed without having to hide our crypto under the mattress and never be able to spend it.

Being an active participant in the Blockchain world, I always look forward to engage with opportunities where I could share my love towards digital transformation.
The presented content may include the personal opinion of the author and is subject to market condition. Do your market research before investing in cryptocurrencies. The author or the publication does not hold any responsibility for your personal financial loss.

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