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How to Sign a WaaS Message

This guide assumes you have completed Create an MPCWallet.

1. Get MPCKey​

To sign a message, use the MPCKey underlying the Address that you generated in Create an MPCWallet.

// Go code in your Proxy server

mpcKeyName, _ := address.GetMpcKeys()[0]

2. Initiate Signature Creation​

Creating a Signature is like creating an MPCWallet in that you initiate, poll, and compute. Initiate with CreateSignature, poll with ListMPCOperations, and compute the operation with the SDK to complete the process.

30-minute limit

Messages must be signed within 30 minutes or they expire.

The operation’s metadata will contain the DeviceGroup you can use to poll with ListMPCOperations.

// Go code in your Proxy server
req := &mpcKeys.CreateSignatureRequest{
  Parent:    mpcKeyName,
  // The payload you want to sign
  Payload: payload,
}

op, err := mpcKeyServiceClient.CreateSignature(ctx, req)

if err != nil {
    log.Fatalf("error initiating signature creation: %v", err)
}

metadata, _ := op.Metadata()

deviceGroupName := metadata.GetDeviceGroup()

3. Poll and Compute MPC Operation​

Signature creation is now underway, and will require MPC participation from your device. Poll for your pending DeviceGroup via your proxy server using ListMPCOperations.

tip

Alternatively, you can use the SDK method pollPendingSignatureAPI, but the proxy server is more secure.

// Go code in your Proxy server

mpcData, err := pollMPCOperations(deviceGroupName, pollChan, 500 * time.Millisecond)

Now use the MPC data in the MPC operation to compute the MPC operation in the WaaS SDK.

// React Native code in your app
computeMPCOperation(mpcData)

4. Get Signature​

Shortly after you compute the MPC operation, the original operation returned from CreateSignature should complete. 

// Go code in your Proxy server
signature, _ := op.Wait(ctx)

signedPayload := signature.GetSignature().GetEcdsaSignature()

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