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Bitcoin Optech
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We provide weekly newsletters, workshops, case studies, and research for the #Bitcoin community.
Bitcoin Optech newsletter #341 is here: - summarizes continued discussion about probabilistic payments - describes additional opinions about ephemeral anchor scripts for LN - relays statistics about evictions from the Bitcoin Core orphan pool - announces an updated draft for a revised BIP process - recaps the "Cluster mempool: introduce TxGraph" PR Review Meeting - adds a Probabilistic payments topic - Optech Newsletter #339 Recap on Riverside Following Oleksandr Kurbatov’s post to Delving Bitcoin last week about emulating an OP_RAND opcode (see Newsletter #340), several discussions were started... Matt Morehouse replied to the thread about what ephemeral anchor script LN should use for future channels (see Newsletter #340). He expressed concerns about third-party fee griefing of transactions with P2A outputs... Developer 0xB10C posted to Delving Bitcoin with statistics about the number of transactions evicted from the orphan pools for his nodes... Mark “Murch” Erhardt posted to the Bitcoin-Dev mailing list to announce that his draft BIP for a revised BIP process has been assigned the identifier BIP3 and is ready for additional review—possibly its last round of review before being merged and activated... 'Cluster mempool: introduce TxGraph' is a PR by sipa that introduces the TxGraph class, which encapsulates knowledge about the (effective) fees, sizes, and dependencies between all mempool transactions, but nothing else. It is part of the cluster mempool project and brings a comprehensive interface that allows interaction with the mempool graph through mutation, inspector, and staging functions... Bitcoin Optech will host an audio recap discussion of this newsletter on Riverside.fm Tuesday at 15:30 UTC. Join us to discuss or ask questions!
Bitcoin Optech newsletter #340 is here: - announces a fixed vulnerability affecting LDK - summarizes discussion about zero-knowledge gossip for LN channel announcements - describes the discovery of previous research that can be applied to finding optimal cluster linearizations - provides an update on the development of the Erlay protocol for reducing transaction relay bandwidth - looks at tradeoffs between different scripts for implementing LN ephemeral anchors - relays a proposal for emulating an OP_RAND opcode in a privacy-preserving manner with no consensus changes required - points to renewed discussion about lowering the minimum transaction feerate - Optech Newsletter #340 Recap on Riverside Matt Morehouse posted to Delving Bitcoin to announce a vulnerability affecting LDK that he responsibly disclosed and which was fixed in LDK version 0.1.1... Johan Halseth posted to Delving Bitcoin with an extension to the proposed 1.75 channel announcement protocol that would allow other nodes to verify that a channel was backed by a funding transaction, preventing multiple cheap DoS attacks, but without revealing which UTXO is the funding transaction—enhancing privacy... Stefan Richter posted to Delving Bitcoin about a research paper from 1989 he found that has a proven algorithm that can be used to efficiently find the highest-feerate subset of a group of transactions that will be topologically valid if the subset is included in a block... Sergi Delgado made several posts to Delving Bitcoin about his work over the past year implementing Erlay for Bitcoin Core... Bastien Teinturier posted to Delving Bitcoin to ask for opinions about what ephemeral anchor script should be used as one of the outputs to TRUC-based LN commitment transactions as a replacement for existing anchor outputs... Oleksandr Kurbatov posted to Delving Bitcoin about an interactive protocol that allows two parties to make a contract that will pay out in a way that neither can predict, which is functionally equivalent to randomly... Greg Tonoski posted to the Bitcoin-Dev mailing list about lowering the default minimum transaction relay feerate... Antoine Poinsot made several posts to the Delving Bitcoin thread about the consensus cleanup soft fork suggesting parameter changes... Bob McElrath posted to Delving Bitcoin requesting developers working on covenant designs to consider how their favorite proposal, or a new proposal, could assist in the creation of an efficient decentralized mining pool... A thread from April 2024 received renewed attention this past month. Previously, Bob McElrath posted about having miners commit to the transactions in their mempool and then only allowing them to include transactions in their blocks that were deterministically selected from previous commitments... Developer Zawy posted to Delving Bitcoin about a mining difficulty adjustment algorithm (DAA) for a directed acyclic graph (DAG) type blockchain... Difficulty adjustment algorithms Difficulty adjustment algorithms (DAAs) are the methods by which mining difficulty is regulated, which affects the average time between blocks, the total amount of block space, and the rate of distribution of new bitcoins (the block subsidy)... Bitcoin Optech will host an audio recap discussion of this newsletter with special guests Matt Morehouse, Bastien Teinturier, Bob McElrath, and Antoine Poinsot on Riverside.fm Tuesday at 15:30 UTC. Join us to discuss or ask questions!
Bitcoin Optech newsletter #339 is here: - describes a vulnerability affecting older versions of LDK - looks at a newly disclosed aspect of a vulnerability originally published in 2023 - summarizes renewed discussion about compact block reconstruction statistics - summarizes popular Q&A from Stack Exchange - Optech Newsletter #339 Recap on Riverside Matt Morehouse posted to Delving Bitcoin to disclose a vulnerability affecting LDK that he responsibly disclosed and which was fixed in LDK version 0.1... Antoine Riard posted to the Bitcoin-Dev mailing list to disclose an additional vulnerability possible with the replacement cycling attack he originally publicly disclosed in 2023... Developer 0xB10C posted to Delving Bitcoin updated stats on the frequency at which his Bitcoin Core nodes needed to request additional transactions to perform compact block reconstruction... Selected Q&A from Bitcoin Stack Exchange: - Who uses or wants to use PSBTv2 (BIP370)? - In the bitcoin’s block genesis, which parts can be filled arbitrarily? - Lightning force close detection - Is a segwit-formatted transaction with all inputs of non-witness program type valid? - P2TR Security Question - What exactly is being done today to make Bitcoin “quantum-safe”? - What are the harmful effects of a shorter inter-block time? - Could proof-of-work be used to replace policy rules? - How does MuSig work in real Bitcoin scenarios? - How does the -blocksxor switch that obfuscates the blocks.dat files work? - How does the related key attack on Schnorr signatures work? Bitcoin Optech will host an audio recap discussion of this newsletter with special guest Matt Morehouse on Riverside.fm Tuesday at 15:30 UTC. Join us to discuss or ask questions!
Bitcoin Optech newsletter #338 is here: - announces a draft BIP for referencing unspendable keys in descriptors - examines how implementations are using PSBTv2 - corrects in depth our description last week of a new offchain DLC protocol - summarizes changes to services/client software - Optech Newsletter #338 Recap on Riverside Andrew Toth posted to Delving Bitcoin and the Bitcoin-Dev mailing list a draft BIP for referencing provably unspendable keys in descriptors... Sjors Provoost posted to the Bitcoin-Dev mailing list to ask about software that had implemented support for version 2 PSBTs in order to help test a PR adding support for it to Bitcoin Core... In our description of offchain DLCs in last week’s newsletter, we confused the new scheme proposed by developer conduition with previously published and implemented offchain DLC schemes. There’s a significant and interesting difference... Changes to services and client software: - Bull Bitcoin Mobile Wallet adds payjoin - Bitcoin Keeper adds miniscript support - Nunchuk adds taproot MuSig2 features - Jade Plus signing device announced - Coinswap v0.1.0 released - Bitcoin Safe 1.0.0 released - Bitcoin Core 28.0 policy demonstration - Rust-payjoin 0.21.0 released - PeerSwap v4.0rc1 - Joinpool prototype using CTV - Rust joinstr library announced - Strata bridge announced Bitcoin Optech will host an audio recap discussion of this newsletter on Riverside.fm Tuesday at 15:30 UTC. Join us to discuss or ask questions!
Bitcoin Optech newsletter #337 is here: - summarizes continued discussion about rewarding pool miners with tradeable ecash shares - describes a new proposal for enabling offchain resolution of DLCs - Optech Newsletter #337 Recap on Riverside Discussion continued since our previous summary of a Delving Bitcoin thread about paying pool miners with ecash for each share they submitted... Developer conduition posted to the DLC-dev mailing list about a contract protocol that allows an offchain spend of the funding transaction signed by both parties to create multiple DLCs... Bitcoin Optech will host an audio recap discussion of this newsletter on Riverside.fm Tuesday at 15:30 UTC. Join us to discuss or ask questions!
Bitcoin Optech newsletter #336 is here: - describes a potential change to Bitcoin Core affecting miners - summarizes discussion about creating contract-level relative timelocks - discusses a proposal for an LN-Symmetry variant with optional penalties - Optech Newsletter #336 Recap on Riverside Abubakar Sadiq Ismail posted to Delving Bitcoin about a bug discovered in 2021 by Antoine Riard that results in nodes reserving 2,000 vbytes in block templates for coinbase transactions rather than the intended 1,000 vbytes... Gregory Sanders posted to Delving Bitcoin about finding a solution for a complication he discovered about a year ago when creating a proof-of-concept implementation of LN-Symmetry... Daniel Roberts posted to Delving Bitcoin about preventing a malicious channel counterparty (Mallory) from being able to delay channel settlement by deliberately broadcasting old states at a higher feerate than an honest counterparty (Bob) is paying for confirmation of the final state... Bitcoin Optech will host an audio recap discussion of this newsletter with special guests Abubakar Sadiq Ismail and Gregory Sanders on Riverside.fm Tuesday at 15:30 UTC. Join us to discuss or ask questions!
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Bitcoin Optech newsletter #335 is here: - links to information about longstanding deanonymization vulnerabilities in software using centralized coinjoin protocols - summarizes an update to a draft BIP about the ChillDKG distributed key generation protocol compatible with scriptless threshold signing - adds a new monthly section summarizing proposals and discussion about changing Bitcoin’s consensus rules - Optech Newsletter #335 Recap on Riverside Yuval Kogman posted to the Bitcoin-Dev mailing list details about several privacy-reducing vulnerabilities in the centralized coinjoin protocols used by current versions of the Wasabi and Ginger wallets, plus past versions of the Samourai, Sparrow, and Trezor Suite software wallets... Tim Ruffing and Jonas Nick posted to the Bitcoin-Dev mailing list a link to the current draft BIP for ChillDKG, which describes a distributed key generation protocol compatible with FROST scriptless threshold signatures for Bitcoin... Changing consensus: - CTV enhancement opcodes - Adjusting difficulty beyond 256 bits - Transitory soft forks for cleanup soft forks - Quantum computer upgrade path - Consensus cleanup timewarp grace period Bitcoin Optech will host an audio recap discussion of this newsletter with special guest Yuval Kogman on Riverside.fm Tuesday at 15:30 UTC. Join us to discuss or ask questions!
Bitcoin Optech newsletter #334: 2024 Year-in-Review Special is here: - notes Bitcoin developments during each month of 2024 - feature: Vulnerability disclosures - feature: Cluster mempool - feature: P2P transaction relay - feature: Covenants and script upgrades - feature: Major releases of popular infrastructure projects - feature: Optech In 2024, Optech summarized more than two dozen vulnerability disclosures... An idea for a mempool redesign from 2023 became a particular focus for several Bitcoin Core developers throughout 2024... Fee management has always been a challenge in the decentralized Bitcoin protocol, but widespread use of contract protocols such as LN-Penalty and ongoing research into newer and more complex protocols has made it more important than ever to ensure users can pay and increase fees on demand. Bitcoin Core contributors have been working on this problem for years, and 2024 saw the public release of several new features that significantly improve the situation... Several developers devoted much of their time in 2024 towards advancing proposals for covenants, scripting upgrades, and other changes that would support advanced contract protocols such as joinpools and channel factories... Optech covered major releases of popular infrastructure projects throughout the year... In Optech’s seventh year, we published: - 51 newsletters - 35 new topic pages - over 120,000 words, a 350pg book equivalent - a wallet guide for developers - over 59hr of podcasts, with 488,000 words of transcripts w/75 guests - 200+ non-English translations Bitcoin Optech will host an audio recap discussion of this special newsletter with special guests Dave Harding, Niklas Gögge, Gloria Zhao, and Brandon Black on Riverside.fm Monday at 15:30 UTC. Join us to discuss or ask questions!
Bitcoin Optech newsletter #333 is here: - describes a vulnerability that allowed stealing from old versions of various LN implementations - announces a deanonymization vulnerability affecting Wasabi and related software - summarizes a post and discussion about LN channel depletion - links to a poll for opinions about selected covenant proposals - describes two types of incentive-based pseudo-covenants - references summaries of the periodic in-person Bitcoin Core developer meeting - recaps the "Track and use all potential peers for orphan resolution" PR Review Meeting - summarizes changes to services/client software - summarizes popular Q&A from Stack Exchange - Optech Newsletter #333 Recap on Riverside David Harding announced to Delving Bitcoin a vulnerability he had responsibly disclosed earlier in the year. Old versions of Eclair, LDK, and LND with default settings allowed the party who opened a channel to steal up to 98% of channel value... A developer of GingerWallet disclosed a method a coinjoin coordinator could use to prevent users from gaining any privacy during a coinjoin... René Pickhardt posted to Delving Bitcoin and participated, along with Christian Decker, in an Optech Deep Dive about his research into the mathematical foundations of payment channel networks... /dev/fd0 posted to the Bitcoin-Dev mailing list a link to a public poll of developer opinions about selected covenant proposals... Jeremy Rubin posted to the Bitcoin-Dev mailing list a link to a paper he authored about oracle-assisted covenants. The model involves two oracles: a covenant oracle and an integrity oracle... Many Bitcoin Core developers met in person in October, and several notes from the meeting have now been published... 'Track and use all potential peers for orphan resolution' is a PR by glozow that improves the reliability of orphan resolution by letting the node request missing ancestors from all peers instead of just the one that announced the orphan... Changes to services and client software: - Java-based HWI released - Saving Satoshi Bitcoin development education game announced - Neovim Bitcoin Script plugin - Proton Wallet adds RBF Selected Q&A from Bitcoin Stack Exchange: - How long does Bitcoin Core store forked chains? - What is the point of solo mining pools? - Is there a point to using P2TR over P2WSH if I only want to use the script path? Bitcoin Optech will host an audio recap discussion of this newsletter with special guests Dave Harding and /dev/fd0 on Riverside.fm Tuesday at 15:30 UTC. Join us to discuss or ask questions!
Bitcoin Optech newsletter #332 is here: - announces the disclosure of a transaction censorship vulnerability - summarizes discussion about the consensus cleanup soft fork proposal - Optech Newsletter #332 Recap on Riverside Antoine Riard posted to the Bitcoin-Dev mailing list about a method for preventing a node from broadcasting a transaction belonging to a connected wallet... Antoine Poinsot posted to the existing Delving Bitcoin thread about the consensus cleanup soft fork proposal. In addition to the already proposed fix for the classic time warp vulnerability, he proposed also including a fix for the recently discovered Zawy-Murch time warp... Bitcoin Optech will host an audio recap discussion of this newsletter with special guest Antoine Poinsot on Riverside.fm Tuesday at 15:30 UTC. Join us to discuss or ask questions!
Bitcoin Optech newsletter #331 is here: - summarizes several recent discussions about a Lisp dialect for Bitcoin scripting - adds a Basic Bitcoin Lisp Language topic - summarizes popular Q&A from Stack Exchange - Optech Newsletter #331 Recap on Riverside Anthony Towns made several posts about a continuation of his work on creating a Lisp dialect for Bitcoin that could be added to Bitcoin in a soft fork... Basic Bitcoin Lisp language (bll) is a proposed scripting language that could be added to Bitcoin in a soft fork... Selected Q&A from Bitcoin Stack Exchange: - How does ColliderScript improve Bitcoin? - Why do standardness rules limit tx weight? - Is the scriptSig spending a P2A output expected to be empty? - What happens to the unused P2As? - Why doesn’t Bitcoin’s PoW algorithm use a chain of hashes? - Clarification on false value in Script - What is this micro tx? - Are there any UTXOs that cant be spent? - Why wasnt BIP34 implemented in the coinbase tx’s locktime or nSequence? Bitcoin Optech will host an audio recap discussion of this newsletter with special guest AJ Towns on Riverside.fm Tuesday at 20:30 UTC. Join us to discuss or ask questions!
Bitcoin Optech newsletter #330 is here: - summarizes a proposed change to the LN spec to allow pluggable channel factories - links to a report and a new website for examining transactions on the default signet that use proposed soft forks - describes an update to the LNHANCE multi-part soft fork proposal - discusses a paper about covenants based on grinding rather than consensus changes - summarizes changes to services/client software - #330 Recap on Twitter Spaces ZmnSCPxj posted to Delving Bitcoin a proposal to make a small set of changes to the BOLT specification to allow existing LN software to manage LN-Penalty payment channels within a channel factory using a software plugin... Anthony Towns posted to Delving Bitcoin a summary of activity on the default signet related to proposed soft forks available through Bitcoin Inquisition... Moonsettler posted to Delving Bitcoin and also the Bitcoin-Dev mailing list a proposal for a new opcode, OP_PAIRCOMMIT, to be added to the LNHANCE soft fork proposal... Ethan Heilman posted to the Bitcoin-Dev mailing list the summary of a paper he coauthored with Victor Kolobov, Avihu Levy, and Andrew Poelstra. The paper describes how covenants can be created easily without consensus changes... Changes to services and client software: - Spark layer two protocol announced - Unify wallet announced - bitcoinutils.dev launches - Great Restored Script Interpreter available Bitcoin Optech will host an audio recap discussion of this newsletter with special guests Vojtěch Strnad, Moonsettler, Brandon Black, Ethan Heilman, and Dusty Daemon on Twitter Spaces Tuesday at 15:30 UTC. Join us to discuss or ask questions! https://twitter.com/i/spaces/1OyKAZQdWWnGb
Bitcoin Optech newsletter #329 is here: - summarizes a new offchain payment resolution protocol - links to papers about potential IP-layer tracking and censorship of LN payments - BTCPay Server security fixes - adds an LN-Penalty topic - adds a Timeout trees topic - Optech Newsletter #329 Recap on Twitter Spaces John Law posted to Delving Bitcoin the description of a micropayment protocol that requires both participants to contribute funds to a bond that can be effectively destroyed at any time by either participant... Charmaine Ndolo posted to Delving Bitcoin summaries of two recent papers about reducing the privacy of LN payments and potentially censoring them... BTCPay Server 2.0.3 and 1.13.7 are maintenance releases that include security critical fixes for users of certain plugins and features... LN-Penalty is a state protocol that penalizes a party who publishes a past state by allowing their funds to be seized by their counterparty... Timeout trees are a type of trustless contract protocol that produces a tree of offchain transactions that only remain safe against counterparty theft for a limited period of time (i.e., they time out)... Bitcoin Optech will host an audio recap discussion of this newsletter on Twitter Spaces Tuesday at 15:30 UTC. Join us to discuss or ask questions! https://x.com/i/spaces/1lDxLlkMpnvxm
Bitcoin Optech newsletter #328 is here: - describes a vulnerability affecting old versions of Bitcoin Core - recaps the "Ephemeral Dust" PR Review Meeting - Optech Newsletter #328 Recap on Twitter Spaces Antoine Poinsot announced to the Bitcoin-Dev mailing list the final vulnerability disclosure predating Bitcoin Core’s new disclosure policy... Ephemeral Dust is a PR by instagibbs that makes transactions with ephemeral dust standard, improving the usability of both keyed as well as unkeyed (P2A) anchors... Bitcoin Optech will host an audio recap discussion of this newsletter on Twitter Spaces Tuesday at 15:30 UTC. Join us to discuss or ask questions! https://twitter.com/i/spaces/1YqGovmrydQKv
Bitcoin Optech newsletter #327 is here: - describes a proposal for timeout tree channel factories - summarizes a draft BIP for proofs of discrete log equivalence to be used when generating silent payments - adds a discrete log equivalency (DLEQ) topic - adds a duplex micropayment channels topic - Optech Newsletter #327 Recap on Twitter Spaces ZmnSCPxj posted to Delving Bitcoin and discussed with Optech contributors a proposal for a new multi-layer channel factory design named SuperScalar... Andrew Toth posted to the Bitcoin-Dev mailing list a draft BIP and a link to an implementation for generating and verifying proofs of discrete log equality (DLEQ) for the elliptic curve used by Bitcoin (secp256k1)... Discrete log equivalency (DLEQ) or proofs of discrete log equivalency (PODLE) is the ability to prove two points on an elliptic curve were both derived from the same private value (such as a private key)... Duplex micropayment channels are bi-directional micropayment channels that use deincrementing relative time locks to ensure the latest state is the first that can be confirmed. Bitcoin Optech will host an audio recap discussion of this newsletter with special guest Andrew Toth on Twitter Spaces Tuesday at 14:30 UTC. Join us to discuss or ask questions! https://x.com/i/spaces/1lDxLlkZXaMxm