Add newsletter #5 2018-07-24

Includes suggested changes by John Newbery

_includes/link-to-issues.md

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+{% assign _issues = include.issues | split: "," %}
+{% for _issue in _issues %}
+[#{{_issue}}]: https://github.com/bitcoin/bitcoin/issues/{{_issue}}
+{% endfor %}

_includes/references.md

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+{% comment %}
+<!--REQUIRES PERIODIC UPDATE: update rpc_version below to latest
+version of BitcoinCore.org's RPC docs-->
+{% endcomment %}
+{% assign rpc_version = "0.16.1" %}
+[rpc fundrawtransaction]: https://bitcoincore.org/en/doc/{{rpc_version}}/rpc/rawtransactions/fundrawtransaction/
+[rpc abandontransaction]: https://bitcoincore.org/en/doc/{{rpc_version}}/rpc/rawtransactions/fundrawtransaction/
+
+

_posts/en/newsletters/2018-07-24-newsletter.md

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+---
+title: 'Bitcoin Optech Newsletter #5'
+permalink: /en/newsletters/2018/07/24/
+name: 2018-07-24-newsletter
+type: newsletter
+layout: newsletter
+lang: en
+version: 1
+---
+This week's newsletter includes information about a new language to describe
+output scripts, an update on Bitcoin Core's support for partially-signed
+Bitcoin transactions, and news on several other notable Bitcoin Core merges.
+
+## Action items
+
+- Bitcoin Core [0.16.2RC2][] released for testing in preparation for a
+  maintenance release that will provide bugfixes and backports.
+  Community testing is highly appreciated.  Note, there was no RC1 due
+  to a metadata problem being detected during the release process.
+
+## Dashboard items
+
+- Transaction fees are lower than they were this time last week.  Anyone
+  who can wait 12 or more blocks for confirmation can reasonably pay the
+  default minimum feerate.  It's a good time to [consolidate UTXOs][].
+
+- The number of [native segwit outputs][p2shinfo bech32] had been
+  increasing steadily over time, but dropped by about 400,000 (80%) this
+  week, possibly due to UTXO consolidation by an exchange.  The average
+  number of new native segwit outputs created per hour remains
+  relatively constant, indicating no obvious decrease in adoption.
+
+## News
+
+- **Bitcoin Optech publicly announced:** we received great coverage in
+  [Bitcoin Magazine][announce bmag], [Coindesk][announce cdesk], and several
+  other publications.  This wouldn't have been possible without the
+  support of our founding sponsors and member companies.  Thank you!
+
+- **First Optech workshop held in San Francisco:** as
+  [previously announced][workshop announce], we held our first workshop
+  in San Francisco last week. There were 14 engineers from Bay Area companies and
+  open source projects in attendence, and we had great discussions about
+  coin selection, replace-by-fee, and child-pays-for-parent. Thanks
+  to Square for hosting and Coinbase for helping with organization.
+
+  If you work at a member company and have any requests or suggestions for
+  future Optech events (be that location, venue, dates, format, topics,
+  or anything else), please contact us. We're here to help our member
+  companies!
+
+- **Coin selection RPC unlikely:** In Bitcoin Core's weekly
+  meeting, Andrew Chow raised the possibility of
+  creating an RPC that would allow users to pass in information about a
+  transaction they wanted to create, including a list of available
+  inputs, and receive back a list of which inputs would be selected by
+  the Bitcoin Core wallet's coin selection algorithm.
+
+    Meeting participants were mostly opposed to providing this feature,
+    suggesting that it would be better if it was a library and that
+    Bitcoin Core's recent and continuing work towards encapsulating its
+    coin selection code would simplify development of a third-party
+    library later.  A particular opposition to the idea was that it
+    might reduce the pace of development for direct users of the Bitcoin
+    Core wallet; as Gregory Maxwell said, "Pressure to maintain a stable
+    interface to [coin selection] would be harmful to the project. [...]
+    I don’t want to hear 'we can't implement privacy feature X because
+    it'll break [the coin selection] interface'."
+
+- **First use of output script descriptors:** Pieter Wuille has opened
+  PR [#13697][] to Bitcoin Core that implements his [output script
+  descriptors][] language for describing which output scripts
+  (scriptPubKeys) a wallet should monitor for.  This particular PR only
+  applies to the recently-added [`scantxoutset`][#12196] RPC but Wuille's
+  ultimate goal is to use this new language elsewhere in the API and "to
+  remove the need for importing scripts and keys entirely, and instead
+  make the wallet just be a list of these descriptors plus associated
+  metadata."
+
+- **BIP174 Partially-Signed Bitcoin Transaction (PSBT) support merged:** this
+  provides a standardized format that multiple wallets can use to
+  communicate information about transactions that need to be signed,
+  so that hot wallets can get signatures from cold wallets or hardware
+  wallets, multisig transactions can be signed by multiple wallets, and
+  multiple wallets can collaboratively create multiparty transactions such
+  as CoinJoins.  Several RPCs are added with this merge:
+  `walletprocesspsbt`, `walletcreatefundedpsbt`, `decodepsbt`,
+  `combinepsbt`, `finalizepsbt`, `createpsbt`, and `convertpsbt`.  For a
+  full description, see PR [#13557][].
+
+## Notable Bitcoin Core merges
+
+*Not including those previously discussed in the News section.*
+
+{% comment %}
+git log --merges b25a4c2284babdf1e8cf0ec3b1402200dd25f33f..07ce278455757fb46dab95fb9b97a3f6b1b84faf
+{% endcomment %}
+
+- [#9662][]: New wallets can now be created with private keys disabled.
+  This is primarily meant for users who want to exclusively use their
+  wallet in conjunction with another program or hardware wallet that
+  stores private keys.  This could also be useful to companies that want
+  to use Bitcoin Core features (like coin selection) by creating a
+  wallet, importing their addresses (but not private keys), and then
+  performing whatever actions they desire, such as using the
+  [`fundrawtransaction`][rpc fundrawtransaction] RPC.
+
+- [#12196][]: New `scantxoutset` RPC method that allows searching the
+  set of spendable bitcoins (UTXOs) for those matching an address,
+  public key, private key, or HD keypath.  The main expected use for
+  this is "funds sweeping" where transactions matching an old wallet are
+  found and transferred to a new wallet.  Although this RPC will almost
+  certainly be included in Bitcoin Core 0.17, it will likely be marked
+  as experimental so that its API can be freely changed in subsequent
+  releases. This API is likely to be
+  updated to support output script descriptors, which is planned to
+  happen before 0.17.
+
+- [#13604][]: Bitcoin-Qt is now built by default in addition to bitcoind
+  on 32-bit ARM systems, and should be distributed by default with the
+  other binaries for that system from BitcoinCore.org for future
+  releases.  Bitcoin-Qt with 64-bit ARM is not yet supported by default.
+
+- [#13298][]: The node now sends all announcements ([invs][inv]) for
+  new transactions to all of its incoming peers at the same time, after
+  a random delay.  Previously, Satoshi Nakamoto [added a feature][rand
+  delay] to Bitcoin (the software) that waited for a different random
+  delay for each peer before sending an announcement so that a
+  transaction would propagate around the network somewhat unpredictably,
+  preventing spy nodes from being able to assume that the first peer
+  they received a transaction from was likely the peer that created it.
+
+    However, later investigators realized that someone operating
+    multiple spy nodes could make multiple connections to each node to
+    increase their chances of being the first to receive a given
+    transaction, allowing the spy to again guess which node create the
+    transaction.  This merge improves the situation by preventing a spy
+    making multiple connections from receiving any more information than
+    a spy with one connection.  Outgoing connections (which are selected
+    by the node itself using certain rules) continue to use the old
+    behavior so that transactions continue to propagate unpredictably.
+
+    This change might increase transaction propagation delay slightly,
+    although developers commenting on the PR think the effect will be
+    minimal.  It may also cause bandwidth usage to be less evenly
+    distributed over time.   However, it could (in theory) end up
+    reducing the number of incoming connections to upgraded nodes, if spy
+    nodes no longer find making multiple connections to be useful,
+    reducing overall wasted bandwidth.
+
+- [#13652][]: The [`abandontransaction`][rpc abandontransaction] RPC has
+  been fixed to abandon all descendant transactions, not just children.
+
+## Coming attractions
+
+Next week's newsletter will feature a field report from Anthony Towns, a
+developer at Xapo, about how they consolidated around 4 million UTXOs to
+prepare for potential future fee increases.
+
+We love getting contributions to the newsletter from member companies. If you'd like
+to share your experiences in implementing better Bitcoin technology, please contact us!
+
+[rand delay]: https://github.com/bitcoin/bitcoin/commit/22f721dbf23cf5ce9e3ded9bcfb65a3894cc0f8c#diff-118fcbaaba162ba17933c7893247df3aR718
+[p2shinfo bech32]: https://p2sh.info/dashboard/db/bech32-statistics?orgId=1
+[consolidate utxos]: https://en.bitcoin.it/wiki/Techniques_to_reduce_transaction_fees#Consolidation
+[0.16.2rc2]: https://bitcoincore.org/bin/bitcoin-core-0.16.2/test.rc2/
+[announce bmag]: https://bitcoinmagazine.com/articles/chaincode-devs-google-alumni-create-industry-group-help-bitcoin-scale/
+[announce cdesk]: https://www.coindesk.com/bitcoins-biggest-startups-are-backing-a-new-effort-to-keep-fees-low/
+[output script descriptors]: https://gist.github.com/sipa/e3d23d498c430bb601c5bca83523fa82
+[inv]: https://bitcoin.org/en/developer-reference#inv
+[workshop announce]: /en/newsletters/2018/06/26/#first-optech-workshop
+
+{% include references.md %}
+{% include link-to-issues.md issues="13697,13557,12196,9662,12196,13604,13298,13652" %}