Multi-Party Computation for DID

[prnk28]

How do we utilize multi-wallet encryption amongst all Motor Nodes connected to a User?

Read some interesting stuff about Multi-Party Computation (MPC). TLDR; MPC enables multiple parties – each holding their own private data – to evaluate a computation without ever revealing any of the private data held by each party (or any otherwise related secret information).

• MPC based Wallets: With an MPC wallet, the private keys and their control are divided between several devices. This means that in order to use the funds in an MPC wallet, all of the devices must be used. (If you see where I’m getting at)
• ZenGo Wallet: This is a consumer-facing application for an MPC-based wallet. Right now, it is a two-part system where your devices communicate with ZenGo’s servers

Solution
Since root level DID is currently supposed to be using the MultiSig mechanism and it is not implemented yet (along with Race conditions/Edge cases). Therefore, we should do some R&D on how MPC could be integrated with a Motor Node for our transactional mechanism and authorization mechanism. This would allow the Libp2p motor host to operate as the most secure Wallet on the market. Along with this, I was thinking that private key generation should be tied to Users Vault Bucket - tangential to how ZenGo is handling it, except the data is retained with the User (Due to our DID mechanism).

Resources

• Go MPC Library and Associated Slideshow
• Go Multi Party Sig
• Awesome MPC
• [WHITEPAPER] MPC Wallet by Unbound
• [ARTICLE] MPC Primer by ZenGo
• [VIDEO] MPC Basics

Diagram(s)

[prnk28]

https://securecomputation.org/

[mcjcloud]

Looking into to MPC more, I don't see how it will be useful to us. Here is what I understand about what MPC does compared with what we need for our use case.

Our Problem

We need a means of sharing encrypted data between authorized devices, when any number of those devices are offline. We need the ability to "onboard" new devices so that they may also read any of that account's data. So to recap requirements:

• Encrypt data from one device and decrypt on another
• Decrypt data while all other devices are offline
• Add new devices which can also decrypt that data when all devices are offline

MPC

MPC is a mechanism which allows sensitive information to be withheld, but still used to compute the result of a function on that information. Any invocation of MPC requires that all parties involved be online. It also is not a quick process. So the issues this creates with our use case is:

• Data will not be readable when other devices are offline
• Reading data will be very slow
• Adding new verification methods will be slow and require all other devices to consent

[mcjcloud]

MPC doesn't really make us any more decentralized than we are. Our whole infrastructure is decentralized, so storing keys in buckets/objects doesn't centralize them. You mentioned we no longer need a trusted authority for key generation, but that's already how it works. Key generation is done by motor, no "authority".

I see the slowness and the fact that every device has to participate in the decryption of data a non-starter. It may be secure but it will have a bad user experience.

Lastly, in all my researching I don't see anything concrete on how MPC will actually create a shared key. If it does actually do this, it seems much more efficient to just pass a shared key between two devices than to go through MPC.

[joshLong145]

MPC doesn't really make us any more decentralized than we are. Our whole infrastructure is decentralized, so storing keys in buckets/objects doesn't centralize them. You mentioned we no longer need a trusted authority for key generation, but that's already how it works. Key generation is done by motor, no "authority".

True, i was more thinking of a highway needing to be involved, but in fact it would not need to be invovled in the computation of the keys, it doesn't have to leave the motor.

I see the slowness and the fact that every device has to participate in the decryption of data a non-starter. It may be secure but it will have a bad user experience.

I don't know if all parties will have to participate in decryption as the key will already be created, and stored. which i think means any party can then take advantage

Lastly, in all my researching I don't see anything concrete on how MPC will actually create a shared key. If it does actually do this, it seems much more efficient to just pass a shared key between two devices than to go through MPC.

https://github.com/taurusgroup/multi-party-sig is an implementation of multi party signing using MPC. this uses ECDSA or Schnorr signatures as key types. this supports both two party and multi party key generation.

[mcjcloud]

I don't know if all parties will have to participate in decryption as the key will already be created, and stored. which i think means any party can then take advantage

How does each device get the generated key? What's the point of having MPC generate a key if it's not involved in the distribution?

[joshLong145]

How does each device get the generated key? What's the point of having MPC generate a key if it's not involved in the distribution?

You are right in that each party member is only given a single portion of its key. which means we would have to form the entire key private key. however, each party is given the public key and verification methods for each point. I could see this method somewhat simplifying our method of caching encrypted jwk's in a map to a single encrypted jwk but that is i think the biggest optimization it would bring. I am now worried that these curve calculations will be rather taxing and be too slow for our cases.

[mcjcloud]

We can also just use a single JWK without MPC, since we're going to be using a root level key pair.

[mcjcloud]

The one usecase I do see for MPC is for transferring assets like NFTs or aliases on Sonr. This way we can have MFA through multiple devices to authorize those transactions.

[joshLong145]

I think i agree that its a better use case but wouldn't this almost always be just two parties involved?

[prnk28]

Huzzah @mcjcloud was convinced