If you have a geographically distributed multisig, coordinating signing can become a pain. Either you are moving PSBTs around on flash drives or you are doing something awful like emailing them or saving them to the cloud.

Last year, I tried out keet mostly to see if it could work as a way to move psbts around without a third party.

SigningRoomSigningRoom

Here is an interesting solution to the multisig coordination problem:

It seems like a service that let's you encrypt a psbt in your browser and then send it to their server which forwards it to one of the other members of your multisig quorum. It does not require an account nor an email.

It seems like it should work fairly simply. But I am trying to think through the trade-offs. At the least, it seems like the service would know that your IP address is connected in some way to the IP address of the person who joins your signing session.

Also, at least a person like me, is trusting that the code does what they claim:

For all I know, any psbt I upload here is saved.

It says it provides audit logs, which I assume is something I can use to doublecheck that their server is actually doing what they say it's doing.

Seems worth investigating a little (although I'm still pretty happy with a wallet software -> keet --> to other signer's wallet software flow).