What Is MPC?
Multi-Party Computation (MPC) is a cryptographic technique that allows multiple parties to jointly compute a function - in this case, a digital signature - without any single party ever having access to the complete private key. In the JIL Wallet, your private key is never assembled in one place. Instead, it is split into three shards during key generation, and any two of the three shards can cooperate to produce a valid signature. This is called 2-of-3 threshold signing.
How Key Shards Work
The three shards are distributed as follows: one shard is stored on your device (encrypted in secure storage), one shard is held by the JIL key service infrastructure, and one shard is stored in a geographically separate recovery vault. When you sign a transaction, your device shard and the key service shard cooperate through a secure MPC protocol to produce a signature. The recovery shard is never involved in normal operations - it exists solely for account recovery scenarios.
Why No Seed Phrase
Traditional wallets give you a 12 or 24-word seed phrase that represents your entire private key. If someone finds that seed phrase, they have full access to your assets. If you lose it, your assets are gone forever. MPC eliminates this single point of failure entirely. There is no master secret that can be stolen or lost. Even if an attacker compromises one shard, they cannot sign transactions or access your funds because they would need a second shard to meet the 2-of-3 threshold.
Recovery Process
If you lose access to your device, the recovery process uses the recovery vault shard combined with identity verification. You authenticate through your registered email, 2FA, and additional identity checks. Once verified, the recovery shard pairs with the key service shard to restore your signing capability on a new device. A new device shard is generated, and the old device shard is invalidated. This process maintains self-custody - at no point does any single party (including JIL) have enough shards to access your assets without your participation.
Self-Custody Without the Risk
The MPC model gives you the security benefits of self-custody - you control your assets, no custodian can freeze or seize them - without the operational risk of seed phrase management. It is the approach increasingly adopted by institutional-grade wallet providers because it reduces human error, eliminates single points of failure, and supports key rotation and policy enforcement that seed phrases simply cannot provide.