MPC Wallets

Sphere offers an optional Multi-Party Computation (MPC) wallet service that distributes private key control across multiple parties without ever reconstructing the complete key on a single device. This approach provides institutional-grade security while maintaining non-custodial control.

Key Share Distribution

The private key is split into three shares:

1. User Local Share

   • Stored on user's device
   • Used for regular transaction signing
   • Under direct user control

2. Signing Service Share

   • Managed by Sphere's signing service
   • Accessible only by the user
   • Required for transaction authorization

3. Recovery Share

   • Held by Sphere
   • Used only for account recovery
   • Cannot authorize transactions alone

2/3 Threshold System

Transaction authorization requires any two of the three key shares working together. During normal operations, transactions are authorized using the user's local share combined with the signing service share. This allows the system to operate independently of Sphere while maintaining non-custodial control.

In cases where account recovery is needed, the process combines the signing service share with Sphere's recovery share. This recovery process can only be initiated after proper user verification, ensuring accounts can be restored securely when needed.

Security Features

The MPC wallet architecture ensures the private key never exists in complete form on any single device. Users maintain majority control through possession of two shares, while the system provides independent transaction validation and a secure recovery mechanism. This design supports regulatory compliance requirements while preserving security.

This optional MPC service ensures both security and usability while meeting institutional requirements for asset control and recovery procedures. Users can choose to use this service or manage their own keys through other wallet solutions.