COSHV, Taproot, Segwit Only Wallets, MuSig, Segwit v0-v1~ BitcoinOpTech #48

Okay, here's a synthesized summary of the Bitcoin OpTech #48 podcast episode, broken down into the requested sections.

1. Narrative Summary

This Bitcoin OpTech newsletter and accompanying podcast episode dives deep into several proposed Bitcoin upgrades and optimization strategies, with a significant focus on the emerging "commit-now, distribute-later" transaction model and its implementation via a new technique called Check Outputs Script Hash Verify (COSHV). The episode explores how Taproot, SegWit, and other improvements can be leveraged to reduce transaction fees, enhance privacy, and improve the overall efficiency of the Bitcoin network. The discussion highlights the potential for significant cost savings by allowing users to lock in payments during periods of high fees and distribute them later when fees are lower, a method particularly beneficial for scenarios involving multiple recipients. Alongside this, the conversation also touches on technical details surrounding Taproot key encoding, script verification methods, and the importance of supporting diverse address formats to ensure compatibility and future-proof Bitcoin infrastructure. While promising, the episode also acknowledges potential drawbacks and trade-offs associated with these proposed changes, emphasizing the need for careful consideration and refinement.

2. Main Topics Discussed

• Hash Verify Output Commitments (COSHV): A new opcode and technique enabling "commit-now, distribute-later" transactions for significant fee savings.
• Taproot Discussion: Specifically, the "clean stack rule" and its potential extension to all TapScript, along with considerations for Taproot key encoding.
• Transaction Fees: Review of past fee spikes (over $1-$2 in 2017-2018) and strategies for mitigation (better estimation, coin selection, batching, UTXO consolidation, commitment protocols).
• Commit-Now, Distribute-Later Transactions: A method for deferring payment distribution to periods of lower fees, offering substantial savings compared to batching or individual transactions (up to 90% savings).
• COSHV Implementation: Details on how COSHV leverages Taproot and hashing to create a trustless, non-interactive payment distribution system.
• Taproot Addresses and Public Keys: Clarification on the distinction between Taproot addresses and Public Output Keys (POPs).
• "Back 32" Address Formats: The importance of supporting these formats for Bitcoin wallet and service compatibility.
• Script Verification Methods: Discussion of "up cat up code" and "up check sick from stack up code" used in sidechains like Liquid.

3. Key Quotes

• Willi: "This feels like something with marginal cost but also at most marginal benefits." (regarding the clean stack rule extension)
• Mike Schmidt: "High fees are likely to return."
• "This technique allows spenders and receivers to lock in a set of payments during high fees and then only distribute the actual payment when fees are lower."
• "This elimination of the need to interact is a particular highlight of this proposal."

4. People Mentioned

• Jeremy Rubin: Proposed new opcode.
• Russell O'Connor: Suggested extending the clean stack rule and expressed preferences for concise COSHV implementations.
• Peter Willy (Willi): Taproot developer, expressed concerns about the marginal benefits of certain proposals.
• John Newberry: Suggested avoiding placing a specific bit in the script path for Taproot key encoding.
• Mike Schmidt: Presented a video on Bitcoin transaction fees.
• Matt Corallo: Provided feedback on the flexibility of the COSHV proposal.
• Alice: Example sender in the commitment protocol explanation.
• Bob, Charlie, Kendra: Example receivers in the commitment protocol explanation.

5. Bitcoin Price if Mentioned

The episode mentions fees exceeding $1 and $2 during the January 2017 - January 2018 period. Specific Bitcoin prices were not discussed. Other numbers mentioned include:

• 141 virtual bytes
• 0.002 or 1.4 million Satoshi's per kilo of virtual byte
• 349 Satoshi's

I hope this comprehensive summary is helpful! Let me know if you'd like any adjustments or further details.