Registration of MVKs On-Chain

Protocol Rule

This is a protocol rule mandating the on-chain registration of encrypted MVKs as a prerequisite for interaction. The $k_{\text{MVK}, \text{SOL}}$ is registered before deposit, and the $k_{\text{MVK}, U_i}$ is registered before claim. This step enables the Tier 3 compliance mechanism.

Registration Requirements

Solana MVK Registration

• When: Before any deposit transactions
• What: $k_{\text{MVK}, \text{SOL}}$ (encrypted/committed)
• Purpose: Enables deposits from the user's primary Solana address
• Immutable: Cannot be changed once registered

Umbra Address MVK Registration

• When: Before any claim transactions from a specific Umbra address
• What: $k_{\text{MVK}, U_i}$ (encrypted/committed) for the $i$-th Umbra address
• Purpose: Enables claims from that specific Umbra address
• Address-Specific: Each Umbra address requires its own MVK registration

Registration Process

On-Chain Commitment

1. Public Commitment: Creates a public commitment to the MVK without revealing it
2. Cryptographic Binding: Uses cryptographic commitments to bind the MVK
3. Immutable Record: Once registered, the commitment cannot be changed
4. Public Verification: Allows public verification without revealing the MVK

Registration Prerequisites

• Solana MVK: Must be registered before making deposits
• Umbra MVKs: Must be registered before claiming from each Umbra address
• One-Time Process: Each MVK only needs to be registered once
• Address-Specific: Each Umbra address requires separate MVK registration

Compliance Benefits

Tier 3 Compliance Mechanism

The on-chain registration enables:

• Regulatory Compliance: Meets regulatory requirements for transaction monitoring
• Audit Trails: Provides cryptographic audit trails
• Viewing Key Access: Allows authorized parties to view transactions
• Privacy Preservation: Maintains privacy while enabling compliance

Transaction Authorization

• Deposit Authorization: Solana MVK registration authorizes deposits
• Claim Authorization: Umbra MVK registration authorizes claims
• Selective Disclosure: Enables selective disclosure of transaction details
• Compliance Reporting: Supports regulatory reporting requirements

Security Properties

Privacy Protection

• MVK Hiding: The actual MVK is not revealed on-chain
• Commitment Security: Uses secure cryptographic commitments
• Selective Disclosure: Only authorized parties can decrypt/view transactions
• Unlinkability: Registrations do not reveal relationships between addresses

Immutability

• One-Time Registration: MVKs cannot be changed after registration
• Binding Commitments: Cryptographic commitments bind the MVK
• Tamper Resistance: On-chain registrations are tamper-resistant
• Permanent Record: Creates permanent, verifiable records

Implementation Details

Registration Transaction

• Commitment Creation: Generates cryptographic commitment to MVK
• On-Chain Storage: Stores commitment on-chain
• Verification: Allows public verification of commitment validity
• Gas Costs: Requires gas fees for on-chain storage

Viewing Key Access

• Authorized Access: Only holders of the MVK can decrypt transactions
• Selective Disclosure: Enables disclosure to authorized parties
• Compliance Tools: Supports regulatory compliance tools
• Audit Capabilities: Enables transaction auditing when authorized