Dialogue with Mysten Labs Chief Cryptographer: How does cryptographic innovation become the core of Sui's design?

In this article, we talk to Kostas Chalkias, co-founder and chief cryptographer at Mysten Labs, about how cryptographic innovation is at the heart of Sui's design, and why are upcoming features so exciting?

**Q: Can you briefly explain the role of cryptographers in building blockchains? **

A: I actually worked with one of Satoshi Nakamoto's first developers (Mike Hearn), I have a PhD in cryptography, and before the blockchain era, my focus was mostly academic boundary. Because of this involvement, I can accurately tell you that crypto plays a role for blockchain infrastructure companies, generally broken down into three key roles.

The first is research, you have to be innovative in cryptography because it's usually very advanced math, part of that is finding cool new algorithms, but also research into breaking algorithms. My previous role at a blockchain company involved reviewing cryptography implementations and being a white hat hacker looking for attacks against them. What you do is "You're a mathematician, you're a cryptographer. Go look at this particular implementation of a digital signature algorithm or random beacon or whatever. Check that everything works." That's the domain of research.

The second is implementation, the concept of applied cryptography. Applied cryptographers do get requests from product teams -- "hey, we want a new faster signature scheme, or we want to create a new privacy feature for our clients or customers or the community." And then An applied cryptographer not only designs something, researches it, but also implements it. Sometimes an applied cryptographer also has to be a very strong software developer, requiring novel optimizations in coding.

The last is to create new products and put forward their own innovative ideas based on the primitives understood by cryptographers.

**To sum up, we balance research, implementation, and product, which is the role of a typical blockchain cryptographer. **

**Q: Is it usually the same person who can do all three? Or divided into groups to implement? **

A: For Sui, because we introduced so many innovations, we needed multiple people working on many workflows. I'm the lead cryptographer at Mysten Labs and one of the founders of Sui, so I'm involved in most of the work. However, you can't do everything alone and I'm still learning from my team.

We don't just use one programming language. For example, using the Rust language for a proof of concept, but then we realized that most people on the web are using JavaScript or TypeScript, and cryptographers can't write everything by themselves. But you can't delegate to a generalist like a software engineer, because some optimizations require knowledge of advanced mathematics and cryptographic primitives, or you may need to interact with some libraries that you are not familiar with, so you need someone else to take over the work.

Our research team totals around 10 people and works on innovation and implementation on a daily basis. We have these "smart" minds, and sometimes I'm the one who comes up with ideas, and sometimes I'm following the direction of other crypto experts. Our team can help with implementation, or provide resources or provide tips on how to expand and apply a cool idea.

Two eyes are not enough, because cryptography is an extremely critical part of the blockchain infrastructure. If something goes wrong, it may be GAME OVER, so more eyes are needed. Plus, a lot of innovators are needed.

**Q: What are the key developments and impacts of external research applied in Sui's design? What are the key innovations in the internal dialogue? **

A: In terms of cryptography, external signals that have influenced us are the evolution of technologies such as zero-knowledge proofs, and general privacy-preserving techniques proposed in the literature. Not only the blockchain is doing cryptography, but there are also research institutions and university departments around the world doing theoretical work. Personally, I think Mysten Labs is very good at finding new theories in areas that have never been implemented before, some of these assumptions may not be accurate, but we combine them with our existing technology, and ultimately propel us to create a novel product.

**Sui has a new feature, Zero Knowledge Login (ZK Login), which came into being like this. Some technologies were proposed externally, but not enough to provide a seamless authentication mechanism for the L1 blockchain, we invented new features on top of it, which is an internal vertical of applied research, and finally, we came up with a complete solution plan. **

We're not a university, we're not just theory, we need to implement something production-ready, so we get feedback from internal and external discussions. A lot of times we read scientific papers, we attend events, we are reviewers and presenters, we receive feedback. Obviously, we convert all of these to implementation on Sui.

I realize that some of our code is then used by other people, other companies, or even people outside our industry, and you will end up seeing big companies take that code and inject it into their own infrastructure, not necessarily a blockchain foundation facility.

Internal innovation is often triggered by product teams. They'll come to us and say, "That's not possible at the moment, we haven't seen the research on this. Can you figure this out?"

For example, the interesting problem of enabling discoverable blockchain addresses but with privacy. How can I get something sent to your email or phone number even before you create an account? Imagine a Venmo-style feature where I send you assets and then go get them when you realize they're there. Solving this problem requires brainstorming internally about how to do it right with a privacy mindset. Taking theory from the outside, we combine all of this into a set of tools. Most of the time we're actually pretty successful at that. We try to solve the above problems, and it is rare to encounter a product problem without a solution.

**Q: How does Move help you create these cryptographic innovations and provide a more secure experience for developers using Sui? **

A: I used to be a Solidity developer, writing Ethereum contracts, and I was also passionate about breaking smart contracts on Ethereum. My first job was auditing lottery contracts on Ethereum, and I managed to destroy some algorithms. At the time, you could almost say that randomness algorithms were unfair and opaque. This actually taught me that smart contract developers are usually engineers who write small scripts. Smart contracts are not big programs, nor are they complex databases. Usually, someone with just a few days of training can write a smart contract and deploy it, but this requires very careful auditing, and there may be hidden pitfalls in web2 - web3 interactions.

We realized that on Ethereum, some of Solidity's security features were problematic due to two particular factors. First, engineers are optimizing compression to reduce gas costs, which may cause users to miss some content because edge cases are not covered. And there is also the problem of re-entry attacks. It's like one smart contract paying another smart contract without updating its state. This attack vector has caused significant financial losses in the past, including the Ethereum DAO many years ago, which resulted in an Ethereum fork.

**Move doesn't have these issues, especially for reentrancy issues, we protect the source code from scratch. We also made a lot of changes to the original Facebook Move by creating a more object-centric Move language, which helped a lot with code reusability. Instead of copy-pasting smart contract code, and then maybe making some tweaks, you can call the original code and get better consistency guarantees. **

Also, in Move, we have objects for everything. In Solidity, when you transfer something from one contract to another, you usually don't know what it is without context. Is this the address? Is this a number? Is this an image URL? When you treat everything as objects, similar to Java and C++ and all object-oriented languages, you can first convert your existing client-side projects to a smart contract-based world without worrying about triple-optimized compression mechanisms. Because you can literally see, this is a "tiger" object, I'm transmitting a "tiger" object to you.

What about cryptography? When you own the items, when I send something from one wallet to another address, you get a popup that says "You are transferring a tiger NFT. This tiger NFT has X characteristics". Thanks to the object-centric design, no matter what object you're touching, you can see exactly what you're doing, which can help you identify any problems with your transactions. Many users are lured by malware or apps that try to convince you to sign something you don't want signed in other blockchain wallets. But with Move, it's a bit more difficult, and the user can clearly see what's going on, which enhances end-user security.

Another thing that really helps in designing more interesting and cool algorithms is the parallelization enabled by objects. Let's say I have some bills, a $10 bill and a $100 bill. I can do this in parallel if I offer bills to two people next to me.

On Ethereum, the basic concept is a central account balance from which you can transfer things. So if I want to send or receive funds, I have to order these transactions, I will first send $100, then submit a $10 transaction, at the same time if someone sends me funds, all 3 transactions must be sequenced, this process is expensive of.

That's where we get all the cool stuff from the Move language, and as cryptographers we can use the parallelization and object-oriented programming that Move provides to create better security, cooler innovative algorithms. That's the whole idea. For example, we created a lottery program. While it may seem easy at first glance, to be honest, getting it right is often very, very difficult, especially when building multiplayer lotteries with complex edge cases, which is where good cryptographers shine. We need some randomness, you need to buy lottery tickets that can be bought in parallel. How do you do this on the blockchain? Move and its available cryptographic primitives help provide a better and more secure crypto ecosystem.

I'm well aware that something like a lottery system can be used in a product where, say, 300 tickets are available, but thousands of people want them, and you want them to be randomly distributed? This system is the foundation of Sui, and any company can add it to their products.

The nice thing here is that, due to the object-oriented nature of Sui, you can call the same contract from many different other smart contracts. We have the concept of composability, which actually helps you use the same lottery ticket in two different lotteries, which is great for creating new experiences that didn't exist before.

In gaming, you need randomness, and Sui is actually one of the best blockchains out there. For a board game, even chess, which seems like a deterministic game, you need to know who goes first. Who is white and who is black (in chess, as we know, white has the advantage), it requires some transparency to correctly match different players in the same game. There are also government apps. Imagine the tax office is doing some statistical sampling and selecting who to audit. Can they really provide evidence that statistical sampling was done in a fair and transparent manner?

If there exists an algorithm with undeniable transparency that provides good randomness that cannot be changed by the organizers, then every lottery or random sampling will have a new fairness.

**Q: You recently wrote a tweet discussing the importance of storing NFTs on-chain so they remain dynamic and change over time. Can you share more about this perspective, specifically how Sui's data structure enhances the utility of NFTs? **

A: This is a hotly debated topic. I'm trying to explain that different infrastructures enable NFT properties differently, and when it's just a static image, when you're not doing any high-traffic operations on that image, the traditional structure is really good. But in some cases, such as games, players hope to get more benefits from NFT, then the traditional structure of NFT is not good enough.

Sui has some algorithms that allow for dynamic NFTs whose fields are updated every time a transaction occurs. When you play a game, you have a hero, you win, pass a level, you may get some new weapons or powers, all of which can be recorded in the state of the blockchain and create a kind of A whole new genre. In addition, because the storage cost on Sui is cheap, NFT can be stored on the chain. This makes it easier to read and write different smart contracts on-chain and enables composability.

On other chains you will face a problem because the changes are not in the state. For another smart contract to read your contract, they need to know your structure, you need an off-chain parser, which creates some UX complications. There's also conditional logic in some cool apps where you don't know which NFT you're touching at the time of submitting a transaction, so what can I offer from the off-chain world, it's not easy to scale.

There is also the issue of threat models, and the fact that some specific applications may tolerate compression and off-chain storage. But actually, when we store something off-chain, we are changing the threat model. The reason is usually centralization, imagine if one day you store it in AWS and then... Amazon goes down. Amazon is a single company, if it goes down and you can't access that particular off-chain data, you can't use it on-chain; and even if you could, you'd even need the data to generate proof that you actually own the off-chain data because sometimes You just have to prove it, right? To prove it, you need to get the content from AWS, then hash it and send a very small amount of data into the blockchain, which is verified to some extent, but if you don't have the data, you can't prove it What is the content of my NFT.

So there is some centralization problem, although some people say it is not, because we can store it in different places. I agree that if we can manage to have a specific design, all these threat models are encoded into the blockchain, but the other problem is the delay, in the practice of the chain, we need to get the content with the minimum delay, if put NFT is stored on other chains, which will double the delay. This is not what we want. We hope that everything is stored on the chain while reducing latency.

**Q: What are you most excited about for Sui's future? **

A: This is my favorite question. The main reason I joined Mysten Labs is that I prefer a place where innovation drives product development. We are delivering something new to the community. I even named my son Kryptos.

If you're asking me specifically about Sui's encryption innovations, one thing's for sure, we're allowing a lot of ways to authenticate. Typically, most blockchains only support one signature algorithm, Ethereum has its own, and Cardano and Solana support another. We are trying to make Sui talk to other public chains, which means we allow all existing algorithms, which means we are compatible with more wallets. Existing wallets don't need to reinvent the wheel, you like the algorithm based on Ethereum, we support it, so go ahead and use it. You use an iphone, then you don't even need a wallet, iPhones and more advanced Android devices have this security chip built in that only supports specific algorithms, and we support that.

Then we also have the concept of multi-signature itself, if you pay attention to security, the authentication part of cryptography, which is one of Sui's flagship features, will create a new authentication experience.

Another thing that I personally really like is that we have introduced zero-knowledge proofs, privacy-preserving technology inside Sui from day one. So people can now create a KYC system with as much privacy as possible, they can even create confidential transfers of amounts, while also giving them the opportunity to comply with laws and auditors, we put everything there for developers use. **

In addition to all these algorithms, our developer solutions engineering team actually provides really good support. We work every day with teams that are not versed in cryptography, they don't have cryptographers, but have some really cool ideas, and if we get some feedback, we help them implement, something is not available or there is a problem, we Also solve them with great speed.