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137 lines
6.6 KiB
Markdown
137 lines
6.6 KiB
Markdown
# Zombie Channel Recovery
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## Read me first
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It's useful to understand Zombie Channel recovery is one of the latest
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"desparate" steps in recovering balances. Basically the channel states are not
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known anymore: no one knows what the balances were (there is no channel DB,
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static channel backup did not work, force closing was not possible).
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This means:
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1. You have to find the peer (which, if you want to do a zombie recovery, was
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probably offline if you tried to recover)
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2. You have to find a way to contact this peer (twitter, email, ...)
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3. You and your peer will have to negotiate a closing state: you only know the
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total channel size, and neither of you knows with good confidence who owes
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what. _(Because if you did, you would be able to restore using the static
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channel backup or channel DB.)_ There might be some guessing involved here,
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or maybe you want to do a 50:50 split.
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## Recovery steps
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Preparation:
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* Make sure you have your seed words ready, you will need these to generate
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addresses and prepare keys
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* *Got a request from a counterparty* to prepare keys? Skip to step 4 below.
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* If you already have a way to contact your peer you can create your own match
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file (see ["File format" section](#file-format)) and skip to step 3 below.
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Steps:
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Below image is a simplified version of the steps described below the image.
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1. _(Optional -- only needed if you have no contact with the remote party)_
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Register at [node-recovery.com](https://node-recovery.com). This website
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helps you connect to peers, for recovery. You enter your public key and some
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way to reach you. Hopefully, a peer with whom you have a "crashed" channel,
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will also register. The site will inform you of the peer's contact details,
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and will send channel information.
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2. Got a message about a match? Congrats! You might be able to fix something
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together. Have a look in the recovery file, and look up the mentioned
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channel(s). Node-recovery has looked back at _their_ channel database and
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guessed if the channel needs to be recovered. Please check this, because if
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the guess was wrong, and the channel is active, you do not need to do this
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recovery at all and exit this guide! If you do not see it on your (recovered)
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node, continue:
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3. Send/upload the JSON file(s) to your node. If you open the JSON file(s), you
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will see your own node ID (and contact info) and the peers'. [Download or
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install chantools](https://github.com/lightninglabs/chantools#installation).
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Technically, you do not _need_ to install `chantools` on the same machine as
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your node. Maybe you do not feel confident entering your seed words on your
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node and want to do this someplace else.
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4. Prepare the keys. Both parties will need to do this. The payout address is a
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bitcoin address your sats will be sent to if you both agree on the offer
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(step 6). The final argument must be the match file, which you got in email.
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```
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chantools zombierecovery preparekeys --payout_addr bc1xxx --match_file /tmp/match.json
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```
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5. The command will output a file in the `results/` folder (relative from where
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you ran the command, so after the command finished you can probably do
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`cd results/` to go to the results folder. Type `ls` to view the files. You
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can view the result in a text editor (`nano preparedkeys*`), it's regular
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readable text. It has the contact info of the counterparty. Now is a good
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time to contact the peer. You can attach your preparedkeys file and propose a
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fee rate (sat/vB). Ask them to prepare keys too.
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6. Either your counterparty or you will make an offer. As explained in the
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["Read me first" section](#read-me-first), there might be some guessing
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needed here. Basically the offer proposes a way to split the channel balance
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among you and your peer. If you sent your preparedkeysfile, your counterparty
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has enough information to create an offer. If they send their
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preparedkeysfile to you, you can create the offer. This has a split, which
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you might need to discuss with your peer. Either way, the command to advance
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to the next step is:
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```
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chantools zombierecovery makeoffer \
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--node1_keys preparedkeys-xxxx-xx-xx-<pubkey1>.json \
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--node2_keys preparedkeys-xxxx-xx-xx-<pubkey2>.json \
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--feerate 15
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```
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7. The output is a PSBT. It's signed by the party which created the offer. This
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must now be signed by the other party (thereby accepting the offer):
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```
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chantools zombierecovery signoffer \
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--psbt <offered_psbt_base64>
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```
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8. After signing, the transaction can be broadcast. From the PSBT (_partially
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signed_ bitcoin transaction), by signing, you have now (together) created a
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proper bitcoin transaction. An offer has been made, you have agreed on what
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split ("piece of the pie") goes to whom, created a transaction, signed it.
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This completed transaction can now be sent, for example using
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`bitcoin-cli sendrawtransaction`.
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## File format
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For reference, the file format of the "match" file is below. If you get a match
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from node-recovery.com, the file looks like below example. It's human-readable
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JSON, and you need to open the file to see the contact details. Use any plain
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text editor to open the file.
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Components:
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* `node1` and `node2` are the peers of the channel, with contact details. This
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is not needed by `chantools`, you will use it to contact your peer.
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* Then there is a list of channels, often just one though. It has metadata as
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seen by the network.
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* As you are taking the steps above, the file format will be appended. For
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example, after step 4 (preparing keys), the file will have a list of
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`multisig_keys` for the node who prepared the keys.
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```json
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{
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"node1": {
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"identity_pubkey": "03xxxxxx",
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"contact": "contact information for node 1, not needed by chantools itself"
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},
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"node2": {
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"identity_pubkey": "03yyyyyy",
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"contact": "contact information for node 2, not needed by chantools itself"
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},
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"channels": [
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{
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"short_channel_id": "61xxxxxxxxxxxxx (optional, numerical channel ID, can be found on 1ml.com)",
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"chan_point": "<txid>:<output_index> (also called channel point on 1ml.com)",
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"address": "bc1q...... (the channel's output address on chain, find out by looking up the channel point on a block explorer)",
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"capacity": 123456
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}
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]
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}
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```
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It's encouraged to look at the file, and what the files look like after doing
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each of the steps.
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## More info
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_More info at the help output of `chantools zombierecovery --help` or the
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generated [documentation for the zombierecovery
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command](chantools_zombierecovery.md)._
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