Questions about Full Node and Electrum Server Visibility

Hey everyone, I have a couple of questions about Full Nodes and Electrum Servers if that's cool. 1) When I connect to a full node, what can the owner see? 2) What about connecting to an Electrum server? What info can they access?

It's pretty straightforward. The node owner can see your public IP address. That's why people use things like VPNs or Tor to hide their IP... Also, they get info on your node's compatibility and any transactions you send out. Just keep in mind they can rebroadcast those if they're unconfirmed.

To break it down: 1) They get your IP, maybe your Tor exit node, the version of your node, whether you're just sending blocks or also transactions, and some other stats like your blockheight and min fee. 2) For Electrum, it sees your IP, public keys, and transaction history for all active addresses in your wallet. So yeah, they can track quite a bit.

Can you connect a full node to a public Electrum server? I’m curious if that even works.

Not really. An Electrum server runs on its own Bitcoin Core node and needs RPC credentials to function. You don’t want to give a random Electrum server access to your Bitcoin Core via those credentials. They usually store those in config files you can't access on public servers.

I doubt Electrum actually sends public keys to servers. All it really needs for transaction history is just the address list. If you're paranoid, run your own full node and an Electrum server to avoid third-party connections.

You can't connect them. Electrum servers use a different protocol compared to Bitcoin nodes. They need their own instance of a Bitcoin full node to fetch info for clients.

The owner can see how long you’re connected, your IP, and they can track your transaction history. But they won’t see your private keys, which is a relief.

Yeah, if you're connecting as an SPV wallet, it asks for block filters and such. But to be precise, it’s about the scripthash... The protocol details are there in the docs.

These two questions feel a bit separate. Are you linking it to your Specter Wallet topic?

If it’s tied to your Bitcoin Core, the owner can see everything except your private keys. It’s like a watch-only wallet for them. Definitely avoid connecting to other people's Bitcoin Core.

I run my own Electrum server but I can't find how to see client IPs. It's open for outside connections, but still unsure how to track anything.

My Electrum server is private, so I don’t announce my availability. I see logs when clients connect, but it’s not public. Just checked my Umbrel box too, it runs Electrs. Might have to dig into its settings.

If Fulcrum tells me to delete the datadir and resynch, does that mean I wipe the Fulcrum_db folder completely?

According to the docs, yeah. Whatever your db folder is named, just clear it out and restart Fulcrum. It’ll take time to rebuild.

No idea why it crashed. It's just for Fulcrum and Bitcoind. Power glitches could be it, or my internet dropped a few weeks back.

You should check the logs in your Fulcrum_db. There may be clues. Also, if you have time, check your drive’s S.M.A.R.T. status.