bitcoinops · jnewbery · Oct 29, 2019 · Oct 22, 2019
diff --git a/_posts/en/2019-10-29-schnorr-taproot-workshop.md b/_posts/en/2019-10-29-schnorr-taproot-workshop.md
@@ -0,0 +1,189 @@
+---
+title: Bitcoin Optech Schnorr Taproot Workshop
+permalink: /en/schorr-taproot-workshop/
+name: 2019-10-29-schnorr-taproot-workshop
+type: posts
+layout: post
+lang: en
+slug: 2019-10-21-schnorr-taproot-workshop
+
+excerpt: >
+  A self-study course for learning about the schnorr/taproot softfork proposal.
+
+auto_id: false
+---
+{% include references.md %}
+
+In September 2019, Bitcoin Optech organized workshops in San Francisco and
+New York City on the schnorr/taproot softfork proposals. The aims of the workshops
+were to:
+
+1. share current thinking in the open source community about the proposals,
+2. give engineers a chance to work with the new technology through interactive
+   jupyter notebooks, and
+3. help engineers take part in the community feedback process.
+
+This blog post contains all of the videos, slides and jupyter notebooks from
+those workshops, so engineers at home can learn about these exciting new
+technologies.
+
+The workshops were split into 4 sections:
+
+1. [Preparation and basic math](#preparation-and-basic-math) - shows how to set
+  up the jupyter notebook environment, gives a refresher on basic elliptic
+  curve math, and introduces tagged hashes.
+2. [Schnorr signatures and MuSig](#schnorr-signatures-and-musig) - describes
+  the bip-schnorr signature scheme and how to use MuSig to aggregate multiple
+  public keys and partial signatures into a single pubkey/signature.
+3. [Taproot](#taproot) - demonstrates how to create and then spend a segwit v1 output
+  using either the key path (where a single signature is provided) or the
+  script path (where a commitment to a single script or multiple scripts is
+  embedded in a public key and later revealed and satisfied).
+4. [Case studies](#case-studies) - demonstrates some practical applications
+  of the new schnorr and taproot technologies.
+
+Slides from all the presentations can be downloaded [here][slides].
+Additionally, Bryan Bishop has provided a [transcript][] of the New York
+session.
+
+## Introduction
+
+[![Introduction](/img/posts/taproot-workshop/introduction.png)](https://www.youtube.com/watch?v=1gRCVLgkyAE&list=PLPrDsP88ifOVTEJf_jQGunDUS05M9GdIC)
+{:.center}
+
+John Newbery gives a summary of why schnorr and taproot are useful technologies
+and explains why Bitcoin Optech created the workshop. He then outlines the
+workshop's aims.
+
+## Preparation and basic math
+
+This section shows how to set up the jupyter notebook, gives a refresher on
+basic elliptic curve math and introduces tagged hashes.
+
+#### 0.1 Test Notebook
+
+Before starting the workshops, users should follow the instructions in the
+repository [README][readme], clone the [workshop repository][] and run through
+the test notebook to ensure that their environment is set up correctly.
+
+#### 0.2 Elliptic Curve Math
+
+[![Introduction](/img/posts/taproot-workshop/elliptic-curve-math.png)](https://www.youtube.com/watch?v=oix8ov9iGgk&list=PLPrDsP88ifOVTEJf_jQGunDUS05M9GdIC&index=2)
+{:.center}
+
+Elichai Turkel provides a refresher on the basic elliptic curve math that will be
+required for this workshop.
+
+#### 0.3 Tagged Hashes
+
+_(No video)_ This chapter introduces _Tagged hashes_, which are used in both
+the bip-schnorr and bip-taproot proposals.
+
+## Schnorr signatures and MuSig
+
+This section explains the bip-schnorr proposal and explains how MuSig can be
+used to aggregate multiple public keys and partial signatures into a single
+pubkey and signature.
+
+#### 1.1 Schnorr Signatures
+
+[![Schnorr Signatures](/img/posts/taproot-workshop/schnorr.png)](https://www.youtube.com/watch?v=wybiVFdknhg&list=PLPrDsP88ifOVTEJf_jQGunDUS05M9GdIC&index=3)
+{:.center}
+
+Elichai explains the mathematics behind schnorr signatures and explains the
+bip-schnorr proposal.
+
+#### 1.2 MuSig
+
+[![MuSig](/img/posts/taproot-workshop/musig.png)](https://www.youtube.com/watch?v=5MbTptrXEC4&list=PLPrDsP88ifOVTEJf_jQGunDUS05M9GdIC&index=4)
+{:.center}
+
+Elichai describes the [MuSig algorithm][musig] (authored by Gregory Maxwell,
+Andrew Poelstra, Yannick Seurin and Pieter Wuille), and shows how it can be
+used to aggregate multiple public keys and partial signatures into a single
+pubkey/signature.
+
+## Taproot
+
+This section explains the bip-taproot and bip-tapscript proposals. It shows the
+format of a segwit v1 output and how such an output can be spent in a key path
+spend or a script path spend. It demonstrates how a tweaked public key can commit to
+one or more scripts, and how the segwit v1 output can be spent using one of those
+scripts.
+
+#### 2.0 Introduction to Taproot
+
+[![Introduction to Taproot](/img/posts/taproot-workshop/taproot-intro.png)](https://www.youtube.com/watch?v=KLNH0ttpdFg&list=PLPrDsP88ifOVTEJf_jQGunDUS05M9GdIC&index=5)
+{:.center}
+
+James Chiang gives an overview of the bip-taproot and bip-tapscript proposals. This
+notebook demonstrates how we'll create transaction outputs, then spend them and
+verify that the spend is valid.
+
+#### 2.1 Segwit V1
+
+[![Segwit Version 1](/img/posts/taproot-workshop/segwit-version-1.png)](https://www.youtube.com/watch?v=n-jAUaSkcAA&list=PLPrDsP88ifOVTEJf_jQGunDUS05M9GdIC&index=6)
+{:.center}
+
+James shows how to create segwit v1 transaction outputs and spend them
+using the key path spend.
+
+#### 2.2 Taptweak
+
+[![Taptweak](/img/posts/taproot-workshop/taptweak.png)](https://www.youtube.com/watch?v=EkGbPxAExdQ&list=PLPrDsP88ifOVTEJf_jQGunDUS05M9GdIC&index=7)
+{:.center}
+
+James explains what a key tweak is, and how a tweak can be
+used to commit to arbitrary data.
+
+#### 2.3 Tapscript
+
+[![Tapscript](/img/posts/taproot-workshop/tapscript.png)](https://www.youtube.com/watch?v=nXGe9_M5pjk&list=PLPrDsP88ifOVTEJf_jQGunDUS05M9GdIC&index=8)
+{:.center}
+
+James discusses how we can commit a tapscript in a segwit v1 output by using a
+taptweak, and how we can spend that output using the segwit v1 key path spend
+rules. He also explains the differences between tapscript and legacy bitcoin
+script.
+
+#### 2.4 Taptree
+
+[![Taptree](/img/posts/taproot-workshop/taptree.png)](https://www.youtube.com/watch?v=n6R15Eo6J44&list=PLPrDsP88ifOVTEJf_jQGunDUS05M9GdIC&index=9)
+{:.center}
+
+James shows how a merkle tree of scripts can be constructed, and how we can
+commit to that tree using a taptweak. He then explains how to spend the output by
+satisfying one of those scripts and providing a proof that the script was part
+of the committed tree.
+
+#### 2.5 Huffman Construction
+
+_(No video)_ This bonus chapter shows how to most efficiently construct a tree
+of scripts by placing scripts that are more likely to be spent closer to the
+root of the tree.
+
+## Case studies
+
+This section gives demonstrations of how the new schnorr/taproot technologies
+can be used to build advanced Bitcoin services and products.
+
+#### 3.1 Degrading Multisig
+
+_(No video)_ This chapter demonstrates a degrading multisig wallet. In all
+cases, the output can be spent with a subset of the 'live' keys, but after some
+timeout, the output can be spent with a mixture of 'live' and 'backup' keys.
+Taproot allows multiple spending paths to be committed to, and only the one
+that is exercised is revealed on chain.
+
+## Summary
+
+[![Summary](/img/posts/taproot-workshop/summary.png)](https://www.youtube.com/watch?v=Q1od076K7IM&list=PLPrDsP88ifOVTEJf_jQGunDUS05M9GdIC&index=10)
+{:.center}
+
+ John concludes the workshop by explaining how you can get involved in the
+community feedback process for these proposals.
+
+[slides]: /img/posts/taproot-workshop/taproot-workshop.pdf
+[transcript]: https://diyhpl.us/wiki/transcripts/bitcoinops/schnorr-taproot-workshop-2019/notes/
+[readme]: https://github.com/bitcoinops/taproot-workshop/blob/master/README.md
+[workshop repository]: https://github.com/bitcoinops/taproot-workshop/
diff --git a/img/posts/taproot-workshop/elliptic-curve-math.png b/img/posts/taproot-workshop/elliptic-curve-math.png
diff --git a/img/posts/taproot-workshop/introduction.png b/img/posts/taproot-workshop/introduction.png
diff --git a/img/posts/taproot-workshop/musig.png b/img/posts/taproot-workshop/musig.png
diff --git a/img/posts/taproot-workshop/schnorr.png b/img/posts/taproot-workshop/schnorr.png
diff --git a/img/posts/taproot-workshop/segwit-version-1.png b/img/posts/taproot-workshop/segwit-version-1.png
diff --git a/img/posts/taproot-workshop/summary.png b/img/posts/taproot-workshop/summary.png
diff --git a/img/posts/taproot-workshop/taproot-intro.png b/img/posts/taproot-workshop/taproot-intro.png
diff --git a/img/posts/taproot-workshop/taproot-workshop.pdf b/img/posts/taproot-workshop/taproot-workshop.pdf
diff --git a/img/posts/taproot-workshop/tapscript.png b/img/posts/taproot-workshop/tapscript.png
diff --git a/img/posts/taproot-workshop/taptree.png b/img/posts/taproot-workshop/taptree.png
diff --git a/img/posts/taproot-workshop/taptweak.png b/img/posts/taproot-workshop/taptweak.png
diff --git a/workshops.md b/workshops.md
@@ -19,22 +19,17 @@ If you have any requests or suggestions for future workshop events, please
 
 *Schnorr signatures* and *Taproot* are proposed changes to the Bitcoin
 protocol that promise greatly improved privacy, fungibility, scalability and
-functionality. These seminar format workshops will include a mixture of
-presentations, coding exercises and discussions, and will give engineers at
+functionality.
+
+Bitcoin Optech hosted two seminar format workshops which included a mixture of
+presentations, coding exercises and discussions, and gave engineers at
 member companies an understanding of how these new technologies work and how
-they can be applied to their products and services. They will also give
+they can be applied to their products and services. The workshops also provided
 engineers an opportunity to take part in the feedback process while these
 technologies are still in the proposal stage.
 
-#### Topics
-
-Optech will present each of the following topics, and then engineers will
-get experience writing code that implements:
-
-- [Schnorr signatures](https://github.com/sipa/bips/blob/bip-schnorr/bip-schnorr.mediawiki)
-- [MuSig](https://blockstream.com/2019/02/18/en-musig-a-new-multisignature-standard/)
-- [Taproot](https://github.com/sipa/bips/blob/bip-schnorr/bip-taproot.mediawiki)
-- [Tapscript](https://github.com/sipa/bips/blob/bip-schnorr/bip-tapscript.mediawiki)
+[All material from the workshops][taproot workshop blog post] is available on this website, so engineers can
+learn about the schnorr/taproot proposals at home.
 
 ## Workshop #2 - Paris, November 12-13 2018
 
@@ -87,3 +82,5 @@ Thanks to Square for hosting the workshop and Coinbase for helping with
 organization.
 
 {% include references.md %}
+
+[taproot workshop blog post]: /en/schorr-taproot-workshop/