Newsletters: add 326 (2024-10-25)

_posts/en/newsletters/2024-10-25-newsletter.md

@@ -0,0 +1,182 @@
+---
+title: 'Bitcoin Optech Newsletter #326'
+permalink: /en/newsletters/2024/10/25/
+name: 2024-10-25-newsletter
+slug: 2024-10-25-newsletter
+type: newsletter
+layout: newsletter
+lang: en
+---
+This week's newsletter summarizes updates to a proposal for new LN
+channel announcements and describes a BIP for sending silent payments
+with PSBTs.  Also included are our regular sections with popular
+questions and answers from the Bitcoin Stack Exchange, announcements of
+new releases and release candidates, and descriptions of notable changes
+to popular Bitcoin infrastructure software.
+
+## News
+
+- **Updates to the version 1.75 channel announcements proposal:** Elle
+  Mouton [posted][mouton chanann] to Delving Bitcoin a description of
+  several proposed changes to the [new channel announcements][topic
+  channel announcements] protocol that will support advertising [simple
+  taproot channels][topic simple taproot channels].  The most
+  significant planned change is to allow the messages to also announce
+  current-style P2WSH channels; this will allow nodes to later "start
+  switching off the legacy protocol [...] when most of the network seems
+  to have upgraded".
+
+  Another addition, recently discussed (see [Newsletter #325][news325
+  chanann]), is to allow announcements to include an SPV proof so that
+  any client that has all of the headers from the most-proof-of-work
+  blockchain can verify that the channel's funding transaction was
+  included in a block.  Currently, lightweight clients must download an
+  entire block to perform the same level of verification of a channel
+  announcement.
+
+  Mouton's post also briefly discusses allowing opt-in announcement of
+  existing simple taproot channels.  Due to the current lack of support
+  for announcements of non-P2WSH channels, all existing taproot channels
+  are [unannounced][topic unannounced channels].  A possible feature
+  that can be added to the proposal will allow nodes to signal to their
+  peers that they want to convert an unannounced channel to a public
+  channel.
+
+- **Draft BIP for sending silent payments with PSBTs:** Andrew Toth
+  [posted][toth sp-psbt] to the Bitcoin-Dev mailing list a draft BIP for
+  allowing wallets and signing devices to use [PSBTs][topic psbt] to
+  coordinate the creation of a [silent payment][topic silent payments].
+  This continues the previous discussion about an earlier iteration of the
+  draft BIP, see Newsletters [#304][news304 sp] and [#308][news308 sp].
+  As mentioned in those earlier newsletters, a special requirement of
+  silent payments over most other PSBT-coordinated transactions is that
+  any change to a not-fully-signed transaction's inputs requires
+  revising the outputs.
+
+  The draft only addresses the expected most common situation where a
+  signer has access to the private keys for all inputs in a transaction.
+  For the less common situation of multiple signers, Toth writes that
+  "this will be specified in a following BIP".
+
+## Selected Q&A from Bitcoin Stack Exchange
+
+*[Bitcoin Stack Exchange][bitcoin.se] is one of the first places Optech
+contributors look for answers to their questions---or when we have a
+few spare moments to help curious or confused users.  In
+this monthly feature, we highlight some of the top-voted questions and
+answers posted since our last update.*
+
+{% comment %}<!-- https://bitcoin.stackexchange.com/search?tab=votes&q=created%3a1m..%20is%3aanswer -->{% endcomment %}
+{% assign bse = "https://bitcoin.stackexchange.com/a/" %}
+
+- [Duplicate blocks in blk*.dat files?]({{bse}}124368)
+  Pieter Wuille explains that, in addition to the current best chain of blocks,
+  the block data files can also include stale blocks or duplicate block data.
+
+- [How was the structure of pay-to-anchor decided?]({{bse}}124383)
+  Antoine Poinsot describes the structure of the [pay-to-anchor (P2A)][topic
+  ephemeral anchors] outputs included as part of Bitcoin Core 28.0's [policy
+  changes][bcc28 guide]. The [bech32m][topic bech32] encoded, 2-byte length, v1
+  witness program was chosen as a `bc1pfeessrawgf` vanity address.
+
+- [What are the benefits of decoy packets in BIP324?]({{bse}}124301)
+  Pieter Wuille outlines design decisions around the [inclusion of decoy
+  packets][bip324 decoy packets] in the [BIP324][] specification. The optional
+  decoy packets can be used to obfuscate traffic patterns to prevent recognition by
+  observers during the key exchange, application, and version negotiation phases
+  of the protocol.
+
+- [Why is the opcode limit 201?]({{bse}}124465)
+  Vojtěch Strnad points out code changes by Satoshi during 2010 that intended to
+  introduce an opcode limit of 200, but due to an implementation error, actually
+  introduced a limit of 201.
+
+- [Will my node relay a transaction if it is below my minimum tx relay fee?]({{bse}}124387)
+  Murch notes that a node will only relay transactions that it accepts into its
+  own mempool. While a user could decrease their node's `minTxRelayFee` value to
+  allow local mempool acceptance, the inclusion of a lower relay feerate transaction
+  in a block would still ultimately require a miner running a similar setting
+  and for average feerates to decrease toward that lower feerate.
+
+- [Why doesn't the Bitcoin Core wallet support BIP69?]({{bse}}124382)
+  Murch agrees that universal implementation of [BIP69][]'s transaction
+  input/output ordering specification would help mitigate [wallet
+  fingerprinting][ishaana fingerprinting], but points out that given the
+  unlikelihood of universal adoption, implementing BIP69 is itself a
+  fingerprinting vulnerability.
+
+- [How can I enable testnet4 when using Bitcoin Core 28.0?]({{bse}}124443)
+  Pieter Wuille mentions two configuration options that enable [BIP94][]'s
+  [testnet4][topic testnet]: `chain=testnet4` and `testnet4=1`.
+
+- [What are the risks of broadcasting a transaction that reveals a `scriptPubKey` using a low-entropy key?]({{bse}}124296)
+  User Quuxplusone links to a recent transaction associated with a series of
+  Bitcoin key-grinding ["puzzles"][puzzle bitcointalk] from 2015 that is
+  [theorized][puzzle stackernews] to have been [replaced][topic rbf] by a bot
+  monitoring the mempool for low-entropy keys.
+
+## Releases and release candidates
+
+_New releases and release candidates for popular Bitcoin infrastructure
+projects.  Please consider upgrading to new releases or helping to test
+release candidates._
+
+- [Core Lightning 24.08.2][] is a maintenance release of this popular LN
+  implementation that contains a "few crash fixes and includes an
+  enhancement to remember and update channel hints for payments".
+
+## Notable code and documentation changes
+
+_Notable recent changes in [Bitcoin Core][bitcoin core repo], [Core
+Lightning][core lightning repo], [Eclair][eclair repo], [LDK][ldk repo],
+[LND][lnd repo], [libsecp256k1][libsecp256k1 repo], [Hardware Wallet
+Interface (HWI)][hwi repo], [Rust Bitcoin][rust bitcoin repo], [BTCPay
+Server][btcpay server repo], [BDK][bdk repo], [Bitcoin Improvement
+Proposals (BIPs)][bips repo], [Lightning BOLTs][bolts repo],
+[Lightning BLIPs][blips repo], [Bitcoin Inquisition][bitcoin inquisition
+repo], and [BINANAs][binana repo]._
+
+- [Eclair #2925][] introduces support for using [RBF][topic rbf] with
+  [splicing][topic splicing] transactions via the new `rbfsplice` API command,
+  which triggers a `tx_init_rbf` and `tx_ack_rbf` message exchange for peers to
+  agree to replace the transaction. This feature is only enabled for
+  non-[zero-conf channels][topic zero-conf channels], to prevent potential theft
+  of funds on zero-conf channels. Chains of unconfirmed splice transactions are
+  allowed on zero-conf channels, but not on non-zero-conf channels. In addition,
+  RBF is blocked on liquidity purchase transactions via the [liquidity
+  advertisement][topic liquidity advertisements] protocol, to avoid edge cases
+  where sellers might add liquidity to a channel without receiving payment.
+
+- [LND #9172][] adds a new `mac_root_key` flag to the `lncli create` and `lncli
+  createwatchonly` commands for deterministic macaroon (authentication token)
+  generation, allowing external keys to be baked into an LND node before it's
+  even initialized. This is particularly useful in combination with the reverse
+  remote signer setup suggested in [LND #8754][] (see [Newsletter #172][news172
+  remote]).
+
+- [Rust Bitcoin #2960][] turns the [ChaCha20-Poly1305][rfc8439] authenticated
+  encryption with associated data (AEAD) algorithm into its own crate, allowing
+  it to be used beyond just the [v2 transport protocol][topic v2 p2p transport]
+  specified in [BIP324][], such as for [payjoin V2][topic payjoin]. The code has
+  been optimized for Single Instruction, Multiple Data (SIMD) instruction
+  support to improve performance across various use cases (see [Newsletter
+  #264][news264 chacha]).
+
+{% assign four_days_after_posting = page.date | date: "%s" | plus: 345600 | date: "%Y-%m-%d 14:30" %}
+{% include snippets/recap-ad.md when=four_days_after_posting %}
+{% include references.md %}
+{% include linkers/issues.md v=2 issues="2925,9172,2960,8754" %}
+[mouton chanann]: https://delvingbitcoin.org/t/updates-to-the-gossip-1-75-proposal-post-ln-summit-meeting/1202/
+[news325 chanann]: /en/newsletters/2024/10/18/#gossip-upgrade
+[toth sp-psbt]: https://mailing-list.bitcoindevs.xyz/bitcoindev/[email protected]/
+[news304 sp]: /en/newsletters/2024/05/24/#discussion-about-psbts-for-silent-payments
+[news308 sp]: /en/newsletters/2024/06/21/#continued-discussion-of-psbts-for-silent-payments
+[core lightning 24.08.2]: https://github.com/ElementsProject/lightning/releases/tag/v24.08.2
+[news172 remote]: /en/newsletters/2021/10/27/#lnd-5689
+[rfc8439]: https://datatracker.ietf.org/doc/html/rfc8439
+[news264 chacha]: /en/newsletters/2023/08/16/#bitcoin-core-28008
+[bcc28 guide]: /en/bitcoin-core-28-wallet-integration-guide/
+[bip324 decoy packets]: https://github.com/bitcoin/bips/blob/22660ad3078ee9bd106e64d44662a59a1967c4bd/bip-0324.mediawiki?plain=1#L126
+[ishaana fingerprinting]: https://ishaana.com/blog/wallet_fingerprinting/
+[puzzle bitcointalk]: https://bitcointalk.org/index.php?topic=1306983.0
+[puzzle stackernews]: https://stacker.news/items/683489

_topics/en/channel-announcements.md

@@ -104,6 +104,9 @@ optech_mentions:
   - title: "LN developers discuss upgrades to the gossip protocol"
     url: /en/newsletters/2024/10/18/#gossip-upgrade
 
+  - title: "Updates to the version 1.75 channel announcements proposal"
+    url: /en/newsletters/2024/10/25/#updates-to-the-version-1-75-channel-announcements-proposal
+
 ## Optional.  Same format as "primary_sources" above
 see_also:
   - title: Unannounced channels

_topics/en/psbt.md

@@ -228,6 +228,9 @@ optech_mentions:
   - title: "BIP353 adds a new standard field to PSBT outputs for DNSSEC proofs"
     url: /en/newsletters/2024/09/06/#bips-1657
 
+  - title: "Draft BIP for sending silent payments with PSBTs"
+    url: /en/newsletters/2024/10/25/#draft-bip-for-sending-silent-payments-with-psbts
+
 ## Optional.  Same format as "primary_sources" above
 see_also:
   - title: Output Script Descriptors

_topics/en/silent-payments.md

@@ -71,6 +71,9 @@ optech_mentions:
   - title: "BitBox02 hardware signing device adds silent payment support"
     url: /en/newsletters/2024/09/20/#bitbox02-adds-silent-payment-support
 
+  - title: "Draft BIP for sending silent payments with PSBTs"
+    url: /en/newsletters/2024/10/25/#draft-bip-for-sending-silent-payments-with-psbts
+
 ## Optional.  Same format as "primary_sources" above
 see_also:
   - title: Output linking

_topics/en/simple-taproot-channels.md

@@ -41,6 +41,9 @@ optech_mentions:
   - title: "Discussion of channel upgrade methods, such as switching to simple taproot channels"
     url: /en/newsletters/2024/05/24/#upgrading-existing-ln-channels
 
+  - title: "Updated channel announcements that include support for simple taproot channels"
+    url: /en/newsletters/2024/10/25/#updates-to-the-version-1-75-channel-announcements-proposal
+
 ## Optional.  Same format as "primary_sources" above
 see_also:
   - title: Taproot

_topics/en/splicing.md

@@ -80,6 +80,9 @@ optech_mentions:
   - title: "Eclair #2861 implements on-the-fly funding using liquidity ads with either dual-funding or splicing"
     url: /en/newsletters/2024/10/04/#eclair-2861
 
+  - title: "Eclair #2925 introduces support for using RBF with splicing transactions"
+    url: /en/newsletters/2024/10/25/#eclair-2925
+
 ## Optional.  Same format as "primary_sources" above
 see_also:
   - title: Interactive transaction construction protocol

_topics/en/v2-p2p-transport.md

@@ -80,6 +80,9 @@ optech_mentions:
   - title: "Rust Bitcoin #2644 adds HKDF component in support of a BIP324 implementation"
     url: /en/newsletters/2024/06/07/#rust-bitcoin-2644
 
+  - title: "Benefits of BIP324 decoy packets"
+    url: /en/newsletters/2024/10/25/#what-are-the-benefits-of-decoy-packets-in-bip324
+
 ## Optional.  Same format as "primary_sources" above
 see_also:
   - title: BIP151