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MPC Wallet (Vault)

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Overview

The MPC Wallet (also called MPC Vault) is a fintech-controlled custody wallet used for stablecoin settlement in FX trading. It uses threshold signing so transactions can be authorized without exposing a single reusable private key. In the StRails FX model:
  • MPC Vault is the custody source for stablecoins such as USDC and USDT.
  • Smart Wallet is the custody source for cNGN.
  • The side sending stablecoins from MPC Vault is the side that must sign.

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Key Characteristics

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What MPC Means Here

MPC (Multi-Party Computation) allows a signature to be produced through distributed key operations instead of using one exposed private key in one location. Practical outcomes:
  • No single key holder can unilaterally move funds.
  • Signing can be policy-gated (manual approval or auto-signing rules).
  • Key material is not handled like a plain private key workflow.

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FX Settlement Model

All LP-to-LP FX settlements involving stablecoin transfer use MPC signing on the stablecoin leg.

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Who Signs

Rule of thumb: whoever is sending stablecoins from MPC Vault signs.

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Wallet Roles

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Setup Flow

The MPC setup flow for FX has three core steps:
  1. Register MPC Vault configuration.
  2. Enable auto-signing.
  3. Set auto-signing threshold.

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1. Register MPC Vault

Register your MPC vault credentials and token wallet mappings so your fintech can participate in FX settlement. This step initializes your MPC configuration and places it in approval flow before activation. Before registration, create and enable your MPCVault API user so you can generate the API token used as mpcVaultApiKey in your configuration. MPCVault API setup guide: How to Enable API - Step 1: Create the API User To obtain callbackClientSignerPublicKey and mpcClientSignerPrivateKey, follow steps 1, 2, and 3 in the MPCVault client signer guide: How to Enable API - Client Signer See: Onchain FX Settings - Register MPC Vault

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2. Enable Auto-Signing

Enable automatic signing for eligible FX transactions so lower-risk trades can proceed without manual approval. See: Onchain FX Settings - Enable Auto-Signing

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3. Set Auto-Signing Threshold

Define the USD value limit for auto-signing. Transactions at or below this threshold can be auto-signed (when auto-signing is enabled), while higher-value transactions stay on manual approval. See: Onchain FX Settings - Set Auto-Signing Threshold

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4. Verify Configuration

Retrieve your FX configuration to confirm vault status, auto-signing state, threshold, and signer infrastructure readiness. See: Onchain FX Settings - Get FX Settings See response fields: Onchain FX Settings - Response (Get Settings)
Critical Whitelist RequirementAfter StRails admin approval, use the returned natExternalIp value from Get FX Settings as the IP address to whitelist in MPCVault.Add this IP in both places:
  • API User IP Whitelist
  • API Client Signer IP Whitelist
Auto-signing will not work correctly until this whitelist step is completed.

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Liquidity Requirements

When placing orders, liquidity is required in the correct wallet: Important:
  • Active orders lock liquidity.
  • Available balance must be treated as total balance minus locked balance.

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Operational Lifecycle

Typical lifecycle for signed settlements:
  1. Trade is locked.
  2. Signing request is created.
  3. Status is tracked by polling.
  4. On-chain transfer is verified.
  5. Settlement state is finalized.
This means completion is based on verified state transitions, not only request submission.

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Security and Control Boundaries

What you control:
  • MPC Vault credentials and authorization posture.
  • Manual approval process (where applicable).
  • Auto-signing thresholds and operational enablement.
What platform enforces:
  • API auth and request validation.
  • Trade-state orchestration and settlement checks.
  • Signing workflow integration and status tracking.

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Wallet Comparison