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BOLT 2&7: Cleaner separation of concerns wrt announcement signatures (#97)

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* BOLT 2&7: Cleaner separation of concerns wrt announcement signatures

So far we did not have any indication on what to do if a node does not
allow announcing the channel and we had a mix of concerns in the
`funding_locked` message, which would also transfer the signatures
needed for the announcement. This is a proposal about splitting the
signatures into their own message, so that simple omission is an
opt-out of announcements, and it does not mix announcement/gossip
stuff into the peer-protocol.

(It also ended up adding a localfeatures flag to opt-into the channel-announcement, and thus creating BOLT 9)
This commit is contained in:
Christian Decker 2017-02-07 01:53:39 +01:00 committed by Rusty Russell
parent fb5e8667bb
commit 4e3ad54a90
4 changed files with 35 additions and 14 deletions
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1
00-introduction.md
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@ -20,6 +20,7 @@ This is version 0.
6. [BOLT #6](06-irc-announcements.md): Interim Node and Channel Discovery
7. [BOLT #7](07-routing-gossip.md): P2P Node and Channel Discovery
8. [BOLT #8](08-transport.md): Encrypted and Authenticated Transport
9. [BOLT #9](09-features.md): Assigned Feature Flags
## Glossary and Terminology Guide

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02-peer-protocol.md
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@ -248,8 +248,6 @@ This message indicates that the funding transaction has reached the `minimum-dep
2. data:
* [8:temporary-channel-id]
* [8:channel-id]
* [64:announcement-node-signature]
* [64:announcement-bitcoin-signature]
* [33:next-per-commitment-point]
The `channel-id` is the unique description of the funding transaction.
@ -261,8 +259,6 @@ index which pays to the channel.
This `channel-id` is used in all messages referring to the channel
from this point onwards.
`announcement-node-signature` and `announcement-bitcoin-signature` are the optional signature for `channel_announcement` as described in [BOLT #7](07-routing-gossip.md#the-channel_announcement-message).
#### Requirements
The sender MUST wait until the funding transaction has reached
@ -289,14 +285,6 @@ re-transmit `funding_locked` if the `channel-id` changes.
If the recipient has received previous `funding_locked` message, it
MUST ignore it in favor of the new `funding_locked`.
The sender MUST set `announcement-node-signature` and `announcement-bitcoin-signature` to the signatures for the
`channel_announcement` message, or all zeroes if it does not want the
channel announced.
The recipient SHOULD fail the channel if the `announcement-node-signature` and `announcement-bitcoin-signature`s are incorrect (and not all zeroes).
The recipient SHOULD queue the `channel_announcement` message for its
peers if it has sent and received a non-zero `announcement-node-signature` and `announcement-bitcoin-signature`.
#### Rationale
If the `minimum-depth` is very low (such as 1), it's possible that
@ -443,8 +431,7 @@ reason to pay a premium for rapid processing.
## Normal Operation
Once both nodes have exchanged `funding_locked`, the channel can be
used to make payments via Hash TimeLocked Contracts.
Once both nodes have exchanged `funding_locked` (and optionally `announcement_signatures`), the channel can be used to make payments via Hash TimeLocked Contracts.
Changes are sent in batches: one or more `update` messages are sent before a
`commit_sig` message, as in the following diagram:

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07-routing-gossip.md
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@ -13,6 +13,23 @@ There can only be one valid `channel_announcement` for any channel,
but multiple `node_announcement` messages are possible (to update node
information), and at least two `channel_update` messages are expected.
## The `announcement_signatures` message
This is a direct message between two endpoints of a channel and serves as an opt-in mechanism to allow the announcement of the channel to the rest of the network.
It contains the necessary signatures by the sender to construct the `channel_announcement` message.
1. type: 259 (`announcement_signatures`)
2. data:
* [8:channel-id]
* [64:node-signature]
* [64:bitcoin-signature]
The willingness of the endpoints to announce the channel is signaled during the connection setup by setting the first bit (`0x01`) in the `localfeatures` field.
Should both endpoints have signaled that they'd like to publish the channel (`localfeatures & 0x01 == 0x01`) then the `announcement_signatures` message MUST directly sent following the `funding_locked` message that established the corresponding channel.
The `announcement_signatures` message is created by constructing a `channel_announcement` message corresponding to the newly established channel, and sign it with the secrets matching their `node-id` and `bitcoin-key`, and send them using an `announcement_signatures`.
The recipient MAY fail the channel if the `node-signature` or `bitcoin-signature` is incorrect.
The recipient SHOULD queue the `channel_announcement` message for its peers if it has sent and received a valid `announcement_signatures` message.
If either endpoints does not signal (`localfeatures & 0x01 == 0x00`) then `announcement_signatures` MUST NOT be sent.
## The `channel_announcement` message
This message contains ownership information about a channel. It ties

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09-features.md Normal file
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@ -0,0 +1,16 @@
# BOLT #9: Assigned Feature Flags
This document tracks the assignment of `localfeatures` and `globalfeatures` flags in the `init` message ([BOLT #1](01-messaging.md)), as well as the `features` field in the `channel_announcement` message and `node_announcement` message ([BOLT #7](07-routing-gossip.md)).
They are tracked separately since new flags will likely be added over time.
The `features` flags in the routing messages are a subset of the `globalfeatures` flags, since the `localfeatures` are by definition only of interest to direct peers.
## Assigned `localfeatures` flags
This flags may only be used in the `init` message.
| Bits | Description | Link |
|------|-------------------------------------------------|---------------------------------------------------------------------|
| 1 | The sending node wishes to announce the channel | [BOLT #7](07-routing-gossip.md#the-announcement_signatures-message) |
## Assigned `globalfeatures` flags