Newsletters: add 79 (2020-01-08)

_posts/en/newsletters/2020-01-08-newsletter.md

@@ -0,0 +1,103 @@
+---
+title: 'Bitcoin Optech Newsletter #79'
+permalink: /en/newsletters/2020/01/08/
+name: 2020-01-08-newsletter
+slug: 2020-01-08-newsletter
+type: newsletter
+layout: newsletter
+lang: en
+---
+This week's newsletter summarizes the final week of the organized
+taproot review, describes a discussion about coinjoin mixing without
+either equal value inputs or outputs, and mentions a proposal to encode
+output script descriptors in end-user interfaces.  Also included is our
+regular section about notable changes to popular Bitcoin infrastructure
+projects.
+
+{% comment %}<!-- include references.md below the fold but above any Jekyll/Liquid variables-->{% endcomment %}
+{% include references.md %}
+
+## Action items
+
+- Bitcoin Optech is planning to hold a third Schnorr and Taproot
+  seminar workshop in London on February 5th 2020. This will cover
+  the same material as the previous two [Schnorr/Taproot workshops][],
+  which is available on this website for home study.
+
+  **Member companies who would like to send engineers to the workshop should
+  [email Optech][optech email]**.
+
+## News
+
+- **Final week of organized taproot review:** December 17th was the
+  final scheduled [meeting][taproot meeting] of the taproot review
+  group.  Pieter Wuille posted the [slides][wuille slides] from a
+  presentation he gave summarizing progress, including text indicating
+  he thought the proposal was "nearly ready".  Wuille also proposed a
+  [minor change][wuille suggestion] to the tapleaf versioning.  Also
+  briefly mentioned was the [discussion][zmn post] started by ZmnSCPxj
+  on the Lightning-Dev mailing list about how precisely taproot could be
+  integrated with LN to provide improved privacy and scalability.
+
+- **Coinjoins without equal value inputs or outputs:** Adam Ficsor
+  (nopara73) started a [discussion][ficsor non-equal] on the Bitcoin-Dev
+  mailing list about two previously-published papers ([1][cashfusion],
+  [2][knapsack]) describing coinjoins that didn't use either equal-value
+  inputs or outputs.  Previous attempts at non-equal mixes were [easy to
+  compromise][coinjoin sudoku], but if an improved method was found, it
+  could significantly improve the privacy of coinjoins by making their
+  transactions look like [payment batching][].  This seemed especially
+  relevant after reports that a popular exchange was investigating users
+  participating in the chaumian-style coinjoins created by Wasabi
+  Wallet.  Although several ideas were discussed, we think the [summary][ontivero summary]
+  by Lucas Ontivero captures the essence of the overall conclusion: "In
+  summary, unequal inputs/outputs coinjoins [knapsack][] is the best we
+  have at the moment ([but] it is not as effective as equal-outputs
+  transactions)."
+
+- **Encoded descriptors:** Chris Belcher [asked][belcher descriptors]
+  for feedback from the Bitcoin-Dev mailing list about base64 encoding
+  [output script descriptors][topic descriptors] so that they're easier
+  to copy and paste (and also so that regular users aren't exposed to
+  their code-like syntax).  At least one reply was opposed to the idea
+  and other replies which did support the idea each proposed a different
+  encoding format.  The discussion to date did not come to any
+  clear conclusion.
+
+## Notable code and documentation changes
+
+*Notable changes this week in [Bitcoin Core][bitcoin core repo],
+[C-Lightning][c-lightning repo], [Eclair][eclair repo], [LND][lnd repo],
+[libsecp256k1][libsecp256k1 repo], [Bitcoin Improvement Proposals
+(BIPs)][bips repo], and [Lightning BOLTs][bolts repo].*
+
+- [C-Lightning #3351][] extends the `invoice` RPC with a new
+  `exposeprivatechannels` parameter that allows the user to request
+  the addition of route hints for private channels to a generated [BOLT11][]
+  invoice.  The user may optionally specify which channels they want to
+  advertise in the invoice, including both public and private channels.
+
+- [LND #3647][] switches from using base64 to hex for the display of
+  binary data in the `listinvoices` RPC.  This is a breaking API change for users of any
+  of the updated fields.
+
+- [LND #3814][] allows the UTXO sweeper to add wallet inputs to a
+  sweep transaction in order to ensure its output meets the dust limit.
+  This is designed to help support the proposed anchor outputs feature
+  (see [Newsletter #70][news70 anchor]) which will need to add inputs to
+  a transaction in order to be able to spend low-value UTXOs.
+
+{% include linkers/issues.md issues="3647,3814,3351" %}
+[Schnorr/Taproot workshops]: /en/schorr-taproot-workshop/
+[wuille slides]: https://prezi.com/view/AlXd19INd3isgt3SvW8g/
+[wuille suggestion]: http://www.erisian.com.au/meetbot/taproot-bip-review/2019/taproot-bip-review.2019-12-17-19.01.log.html#l-8
+[zmn post]: https://lists.linuxfoundation.org/pipermail/lightning-dev/2019-December/002375.html
+[ficsor non-equal]: https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2019-December/017538.html
+[cashfusion]: https://github.com/cashshuffle/spec/blob/master/CASHFUSION.md
+[knapsack]: https://www.comsys.rwth-aachen.de/fileadmin/papers/2017/2017-maurer-trustcom-coinjoin.pdf
+[coinjoin sudoku]: http://www.coinjoinsudoku.com/
+[payment batching]: https://github.com/bitcoinops/scaling-book/blob/master/x.payment_batching/payment_batching.md
+[belcher descriptors]: https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2019-December/017529.html
+[news70 anchor]: /en/newsletters/2019/10/30/#ln-simplified-commitments
+[taproot meeting]: http://www.erisian.com.au/meetbot/taproot-bip-review/2019/taproot-bip-review.2019-12-17-19.01.html
+[ontivero summary]: https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2019-December/017544.html

workshops.md

@@ -12,6 +12,13 @@ and the specific scaling challenges that they are facing.
 If you have any requests or suggestions for future workshop events, please
 [contact us][optech email].
 
+## Workshop #5 - Schnorr and Taproot Seminars {#taproot-workshop}
+
+Bitcoin Optech will host a third seminar workshop on the Schnorr and Taproot
+soft fork proposals in London on 5th February 2020.
+
+Member companies who would like to attend should [contact us][optech email]!
+
 ## Workshops #3 & #4 - Schnorr and Taproot Seminars {#taproot-workshop}
 
 - San Francisco, September 24 2019