--- title: "Co-signed Wallet" description: "Create a co-signed MPC wallet with the Fystack Cosigner mobile app, then withdraw and sign transactions from your phone." url: https://docs.fystack.io/product/co-signed-wallet last_updated: 2026-11-12 --- > ## Documentation index > Fetch the complete documentation index at: https://docs.fystack.io/llms.txt > Use it to discover all available pages before exploring further. # Co-signed Wallet A **co-signed MPC wallet** splits its signing key between Fystack and one or more cosigners you control, such as the **Fystack Cosigner** mobile app. Every key share is required to sign, so Fystack can never move funds alone. This guide walks through the two flows you will use most: 1. **Create a co-signed wallet**: approve the key generation on your phone and back up your key share. 2. **Withdraw and sign**: start a withdrawal on the dashboard and sign it on your phone. > **Note:** Before you start, install the Fystack Cosigner mobile app and connect it to > your workspace. Your phone appears as a cosigner you can pick when creating a > wallet. For a server-side cosigner, see the [Cosigner](https://docs.fystack.io/cosigner.md) > documentation. ## Create a Co-signed MPC Wallet ### Step 1: Open Create Wallet Sign in to the [Fystack dashboard](https://app.fystack.io/), go to **Wallet** in the sidebar and click **Create Wallet**. _Image: Wallet dashboard with the Create Wallet button highlighted_ ### Step 2: Choose Co-signed MPC Switch to the **Co-signed** tab and select **Co-signed MPC**. This wallet type is signed together with your cosigners and works with both a **Mobile cosigner** and a **Server cosigner**. _Image: Create Wallet dialog on the Co-signed tab with Co-signed MPC and HD MPC options_ > **Note:** **HD MPC** creates child wallets under an existing HD master and needs no > extra setup. Use it when you need many wallets, for example one per customer. ### Step 3: Configure Cosigners and Threshold Set up who holds a share of the wallet key: - **Cosigners**: the **Fystack cosigner** is always included. Click **Manage** to add your mobile cosigner. - **Signatures Required**: the number of cosigners that must sign each transaction. With 2 of 2, every cosigner must sign. - **Wallet Name**: a name to identify the wallet. - **Networks**: leave empty to support all networks. The **Compromise resistance** and **Loss tolerance** bars show the trade-off: a higher threshold makes the wallet harder to compromise, but leaves less room if a cosigner is lost. Click **Create**. _Image: Cosigners list with Fystack cosigner and a mobile cosigner, 2 of 2 threshold, and wallet name field_ ### Step 4: Wait for Mobile Approval The dashboard now waits for your cosigner to approve the key generation. Keep this dialog open and pick up your phone. _Image: Create Wallet dialog showing Waiting For Mobile Approval_ ### Step 5: Approve the Key Generation on Your Phone Open the Fystack Cosigner app. The new wallet appears under **Wallet setup** with a **Key generation** tag. Tap it to review: - The wallet name and who initiated the request - The threshold, for example **2 of 2** - What happens next: your device generates and keeps 1 of the key shares for both ECDSA and EdDSA curves. No funds move. Press and hold **Hold to approve**. Tap **Reject** if you did not expect this request. _Image: Cosigner app home with a pending Key generation request for Cosign wallet_ _Image: Pending wallet setup screen with Generate key share details and Hold to approve button_ _Image: Approval recorded and the app generating its key share_ The app runs the MPC key generation ceremony with Fystack. Keep the app open until it finishes. The timeline moves from **Approved by you** to **MPC key generation** and then **Completed**. ### Step 6: Back Up Your Key Share Once your key share is created, the app asks you to back it up. Tap **Turn on auto backup**. The key share is encrypted on the phone and saved to your Google Drive, so: - You have no password to remember - You restore it with your passkey - Fystack can never read it _Image: Back up your wallet screen with Turn on auto backup button_ _Image: Encrypting and uploading to Google Drive_ _Image: Backup screen showing Auto backup is on with passkey and recovery words as restore methods_ The **Backup** screen lists your **Ways to restore**: your synced **Passkey** and your **Recovery words**. Tap **Also save a copy as file** if you want an extra offline copy, then tap **Done**. > **Note:** If you skip the backup and lose your phone, you lose your key share. With a 2 > of 2 threshold, the wallet cannot sign without it. ### Step 7: Confirm the Wallet Is Ready The approval shows as **Approved** in the **Activity** tab, and the new wallet appears in the wallet list marked **Backed up**. On the dashboard, the wallet is listed with the **Co-signed** signing model. _Image: Activity tab showing the approved Wallet setup request_ _Image: Cosigner app listing Cosign wallet as Backed up_ ## Withdraw and Sign Withdrawals from a co-signed wallet need a signature from your cosigner before they are broadcast. ### Step 1: Create the Withdrawal On the [Fystack dashboard](https://app.fystack.io/), open the co-signed wallet and click **Send**. Fill in: - **Asset** and **Amount** - **Transaction Speed**: Slow, Standard, or Fast - **Recipient Address**: enter it or pick one from the **Address Book**. Click **Verify address** to check its risk score. Click **Withdraw**. If the wallet has an approval group, the withdrawal is approved there first. See [Withdrawal](https://docs.fystack.io/product/withdrawal.md) for the full withdrawal options. _Image: Withdraw dialog with USDT on BNB Mainnet, amount, transaction speed, and recipient address_ ### Step 2: Review the Sign Request on Your Phone The Fystack Cosigner app shows a new item under **Sign requests**, and the wallet shows **1 pending**. Tap it to review. Check every detail before you sign: - **Signing input match**: confirms the app independently verified that what it signs matches the transaction shown - **Network**, **amount**, and **token** - **Token contract** and **Recipient** address - **Raw amount** and **Decimals** Press and hold **Hold to sign**. Tap **Reject** if anything looks wrong. _Image: Cosigner app home with a pending Sign request for 1 USDT_ _Image: Sign request details with Signing input match, token transfer, recipient, and Hold to sign button_ > **Note:** Always compare the recipient address on your phone with the address you > entered on the dashboard. Your phone is an independent check: if the two do > not match, reject the request. ### Step 3: Track the Transaction After you sign, the request shows **Signed** with a timestamp. Scroll down to see the decoded **Contract call**, the **Nonce** and **Maximum fee**, and the **On-chain transaction** with its hash. Tap **View on block explorer** to open it. _Image: Sign request marked Signed_ _Image: Contract call details and on-chain transaction hash with View on block explorer link_ _Image: Transaction details on BscScan with Success status_ The **Transactions** tab lists every transfer you signed with its status. Once it shows **Confirmed**, the withdrawal is complete. _Image: Transactions tab listing confirmed transfers_