Also requires a design doc/spec before implementing regarding how this fits into the data store.

Thoughts on implementation approach below.

Sample Usage:

./plasmacli tx broadcast-sigs
./plasmacli tx broadcast-sigs <input1, input2>
./plasmacli tx broadcast-sigs --confirmSigs0 --confirmSig1

Broadcasting Steps as follows:

1. Retrieve confirm sigs from local storage (iterating over inputs - accessing via clistore)
2. Parse confirm sigs (checking for --confirmSig flag usage overwriting confirm sigs)
3. Create new sigMsg containing confirm Signatures
4. Validate sigMsg
5. Broadcast using cli.BroadcastAndAwaitCommit()

Validate sigMsg includes:
{
plasma.Input1
plasma.Input2
}

Handling Steps as follows:
AnteHandler defines sigMsgHandler

1. Retrieves sigMsgSigner
2. Validates Inputs
   2a) validateConfirmSignatures() already exists
   • Checks signer of confirmhash = signer of sigMsg

Add route for sigMsgHandler

1. Receives validated sigMsg
2. Stores Signature type in DataStore - contains {signature, inputs, signer}

@hamdiallam would appreciate insight on other things needed here

We don't need the signer because we want to allow anyone to broadcast the confirm signature. The ante handler would check that the confirm signature is correctly constructed.

Looks good to me