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The case for Threshold Signature Scheme MPC
Threshold Signature Scheme MPC technology is emerging as a leading option that optimizes for a secure and user-friendly Web3 wallet experience.
July 28, 2023
On the blockchain, keys are used to secure and control access to digital assets, verify transactions, and provide cryptographic proof of ownership. Proper key management is an important factor in improving the integrity, confidentiality, and availability of a user’s assets.
Users with accounts on centralized crypto exchanges don’t have to worry about key management. The exchanges handle the keys on behalf of their users.
In contrast, Web3 wallets offer users full control of their funds, making key management an important feature. The most common Web3 wallet architectures are: Externally Owned Accounts (EOA - think MetaMask), multi-signature (multi-sig), smart contract, Shamir Secret Sharing (SSS) Multiparty Computation (MPC), and Threshold Signature Scheme (TSS) MPC. Key management complexity, security trade offs, and costs associated with setup and transactions vary across these different architectures.
As interest in user-managed wallets grows across both end users and organizations looking to build blockchain-connected products, the best fit wallet architecture will depend on user and business needs.
What Web3 wallet key management entails
For builders, choosing a Web3 wallet architecture usually depends on how the key management functionality impacts usability, security, and scalability.
For example, an enterprise business serving thousands or millions of users requires a wallet that can scale—both in number of users and transaction throughput. Such a wallet would need to deliver a simplified user experience, a high level of security, and cost effectiveness. The following table provides an overview of how key management works across the five most common wallet types.
Key management overview by Web3 wallet type
In summary, EOA, multi-sig, and smart contract wallets offer strong security but put the onus on users to safeguard seed phrases and private keys; require users to be technically savvy; or incur transaction fees for every action. On the other hand, MPC wallets minimize user friction and costs, but the SSS architecture has a security vulnerability that TSS MPC does not have: the private key gets reconstructed, creating an attack vector.
TSS MPC is increasingly recognized in the industry for key management functionality that lets users retain full control over their assets with a relatively friction-free, secure, and cost-effective setup.
How TSS MPC optimizes for security, usability, and scalability
It’s worth exploring what makes the TSS MPC architecture a strong contender for the enterprise use case. In particular, this analysis focuses on security, usability, and scalability.
With both SSS MPC and TSS MPC, a single private key is divided into key shares held by multiple entities. Unlike SSS MPC, these key shares are never fully reconstructed into the private key at any point with TSS MPC. Keeping key shares separate from each other—whether at wallet generation or transaction authorization—reduces the possibility of collusion.
A highly secure MPC design is the two-of-two parallel threshold. By creating only two key shares, and requiring both to be used for every transaction, only a minimum number of parties are needed to operate an MPC wallet. One key share used to sign transactions is held by the end user and the other is held by the wallet provider (someone like Portal), making the process simpler than MPC wallet designs with three or more key shares. The party holding the second primary key share can never sign a user’s transaction without them.
MPC wallets do not require seed phrases. Instead, social sign in or biometrics make it faster and easier for users to create a wallet in 30 seconds or less.
Should users ever have to recover access to their accounts, backup key shares are encrypted and stored away from the users’ device, minimizing the possibility of a bad actor getting a hold of both the account on the device and the backup keys.
For enterprise customers, the two-of-two parallel threshold design has a usability advantage over an M-of-N design: it reduces the number of parties that must be vetted and set up to store keys or sign transactions. Devising your own M-of-N design may create potential legal questions that as an app developer you would have to research and decide on your own.
For organizations interested in Account Abstraction, MPC wallets can be set up with Account Abstraction. (Portal offers this capability directly in our SDK. Check out our Account Abstraction documentation or Account Abstraction blog post for more details).
For enterprise customers, the TSS MPC design easily supports thousands or millions of users per organization across ETH and all EVM blockchains without having to worry about lag or latency. No gas fees are required for any TSS operations such as wallet generation, backup, or recovery.
Additionally, organizations can implement flexible policies for generating new key shares with TSS MPC. For example, a business can choose to generate a new set of key shares every time a user logs in and authenticates. Or they can choose to only refresh key shares upon the recovery process. Either setup supports an enterprise-level user base.
Strong security with user-friendly design will drive adoption
As Web3 adoption grows and more industries integrate blockchain technology into their products, a wallet design that balances security with ease of use will be table stakes. Partnering with a company like Portal prepares your business for the future.
Our content is for informational purposes only and should not be taken as financial or legal advice. Refer to our website Terms and Conditions for more information.