The Chaincode Podcast: Recent Episodes

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Rusty drops by to tell us about why privacy and robustness should be prioritized in Lightning.

We discuss:

• LN symmetry (04:39)

  • Do we want LN Symmetry to be symmetrical? (05:12)
  • Listen to the conversation with instagibbs
  • Peer to peer protocol (13:30)
  • CTV (16:54)
  • Pushing privacy and robustness to the front of the line (20:33)
  • The dynamics of developing a spec with commercially associated implementations (22:19)
  • Expecting new implementations (26:22)
  • Privacy revisited (27:02)
  • What broke when fee rate spiked? (31:21)

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Elle Mouton and Oliver Gugger join us to talk with us about the Simple Taproot Channel proposal.

We cover:

• Simple Taproot Channels Overview (1:29)
• What’s the state of the spec? (3:06)
• Changes to the scripts in Taproot Channels (4:31)
• Refresher on CPFP carve-out and Anchor Outputs (8:19)
• Why Anchor Outputs need to use script path spends (10:24)
• Other goals of Simple Taproot Channels (15:52)
• Why do PTLCs need Taproot funding outputs? (16:44)
• Potential updates for the gossip protocol: Gossip 1.5 or Gossip 2.0 (18:13)
• PTLCs (25:22)
• Iterative approach or big push (27:19)
• Recoverability of channel funds (33:06)

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Alekos Filini and Daniela Brozzoni visit the podcast to discuss the Bitcoin Development Kit (BDK). Hang out with them on the BDK Discord.

We cover:

• How BDK started (00:48)
• Why is it named BDK and not the Magical Bitcoin Library? (2:10)
• The first users of BDK (3:30)
• Rust HWI (4:20)
• Built around descriptors (7:15)
• The ideal use case of BDK (7:30)
• Pain points (9:05)
• Why do devs keep building wallets from scratch? (10:05)
• Greenwallet (13:03)
• If you have a working wallet, should you switch to BDK? (16:25)
• HWI complaints (see Python) (17:41)

• BDK 1.0 release features (22:31)

  • Sync
  • Planning module

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Tadge Dryja chats with us about writing the Lightning Network paper and working in the Bitcoin space.

We discussed:

• Could blocks be bigger? (0:59)
• Paper: On the instability of Bitcoin without the block reward (9:49)

• Serving billions with Lightning (10:40)

• The state of the debate when writing the Lightning Network White Paper (13:35)

• Would Lightning be possible without Segwit? (17:20)

• Looking in from outside on a project you started (18:54)

• Trimmed HTLCs: Sending 1 sat vs 100,000 sats (22:02)
• Limitations of the Lightning network (25:31)

• Do high fees break lightning? (28:24)

• LN-Symmetry (Eltoo) (31:50)

• SIGHASH_ANYPREVOUT (33:20)

• Why are soft forks so hard? (34:15)

• What’s your wish list (hardfork wishlist wiki, softfork wishilist wiki) for protocol changes? (36:18)

• coinpools

• Bitcoin needs to become more usable (37:54)

• Tadge's thoughts on Education (44:17)
• MAS.S62: Cryptocurrency Engineering and Design
• Dynamics of working on Bitcoin (47:16)

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Andrew Chow joins us to discuss Bitcoin Core wallet development, PSBT, Output Descriptors, and HWI.

We cover:

• Why do we need a wallet in Bitcoin Core? (0:58)

• Refactoring the Wallet codebase to build Output Descriptors (5:59)Should we rewrite the wallet? (10:30)

• Changes to Coin Selection (11:35)

• Wallet interoperability (17:10)

• Hardware Wallet Integration (HWI) (18:20)

• Partially Signed Bitcoin Transactions (PSBT) (19:01)

• Becoming Maintainer (22:06)

• Tracking the UTXO pool (23:43)

• Main components of the Bitcoin Core Wallet (26:00)

• Who uses Bitcoin Core Wallet? (27:02)

- Survey Results

• What’s the future of the GUI? (29:21)

- Bitcoin Core GUI
 - Bitcoin Core GUI-QML

• Switch to Descriptor-based wallets (32:52)

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Greg Sanders joins us to discuss ANYPREVOUT, ephemeral anchors and LN symmetry (a.k.a. ELTOO).

We chat about:

• Package relay (2:07)

• Pinning attacks (3:14)

• BIP125

• T-Bast’s pinning attack summary

• Mempool policy (4:56)

• Stuffing the mempool - 2017 (5:20)

• Rewrite mempool or make the problem simpler (07:57)

• Package relay RBF A.K.A. V3 (8:38)

• Reducing the standard transaction size to 65 bytes PR (14:25)

• March to LN symmetry (19:07)

• Daric: A Storage Efficient Payment Channel With Penalization Mechanism

• Two-party eltoo w/ punishment by AJ Towns

• BIP118 - SIGHASH_ANYPREVOUT (26:17)

• SIGHASH_NOINPUT

• Softfork and activation history (28:11)

• Ephemeral anchors (32:18)

• op_2 email by Luke

• Is ANYPREVOUT useful outside of LN symmetry? (43:27)

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Sergi Delgado joins us to discuss Watchtowers, his prior work in Bitcoin and Lightning privacy, Python vs. Rust and the impact of Eltoo.

We cover:

• Sergi’s prior research

• Mapping Network Topology Research (02:46)

• TxProbe paper

• Andrew Miller
• Coinscope
• Episode on Address Relay with Martin (04:28)

• Block-only connections PR by Suhas (07:32)

• An Empirical Analysis of Privacy in the Lightning Network (09:18)

• Lightning white paper, 2016 (09:48)

• Security and Privacy of Lightning Network Payments with Uncertain Channel Balances (13:38)

• Episode with Sergei on Probing

• Channel Jamming paper (13:50)

• Episode with Clara and Sergei

• Should we pay for failed payments? (14:19)

• HTLC withholding vs. HTLC hodling (15:48)

• Is Lightning flawed when it comes to privacy? (16:32)

• Watchtowers (17:44)

• Python PoC (21:49)

• ZmnSCPxj’s writing watchtowers

• Building on LDK (24:20)

• Transition to rust (24:45)

• Altruistic towers vs professional services (30:21)

• More privacy considerations in Lightning (34:11)

• Monitoring and reacting paradigm (44:04)

• Storage and Eltoo (50:06)

• Professional tower revenue models - subscription vs. bounties (53:00)

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We continue the conversation with Pieter Wuille and Tim Ruffing and Nesting, ROAST, Half-Aggregation, Adaptor Signatures, atomic swaps and more.

If you have not tuned into the first part of this conversation, we recommend listening to that one first.

We cover:

• Nesting (00:49)

• ROAST (12:09)

• Cross-input Signature Aggregation (18:49)

• Half-aggregation (34:32)

- Half-Aggregation of BIP 340 Signatures and BIP340

• Adaptor signatures and atomic swaps (39:32)

Further resources:

• Stephan Livera Podcast #400 Jonas Nick and Tim Ruffing - Half Signature Aggregation

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Pieter Wuille and Tim Ruffing treat us to a conversation about Schnorr, multi-signatures, MuSig, and more. We covered a lot so this is part one of a two part conversation.

We discussed:

• When to roll your own cryptography (01:31)

• Schnorr Signatures (09:01)

- Why is Schnorr preferable to ECDSA? (10:55)

• Schnorr efficiency improvements (15:52)

• Multisigs (23:16)

• MuSig (25:07)

- Yannick Seurin

- Rogue key attack or key cancellation attack (31:00)

- Bellare-Neven (32:12)

• Interactive versus non-interactive protocols (35:30)

• FROST (42:42)

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Clara and Sergei stop by to chat about their recent proposal on mitigating jamming attacks in the Lightning Network. We talk unconditional fees, local reputation, the impact on decentralization and UX, and the state of Lightning in general.

We discuss:

• What is jamming and why is it free? (03:43)

• How our jamming project started (06:44)

• Prior work on jamming (08:00)

• The desired properties of a solution (09:57)

• Reputation (12:47)

• Centralization concerns (14:17)

• Unconditional fees (19:25)

• How are unconditional fees delivered? (23:31)

• UX implications (24:45)

• Moving research results towards implementation (27:15)

• Effects on balance probing (29:21)

• Lightning as a messaging network (30:46)

• Effects on watchtowers (32:57)

• Reviews and feedback so far (34:17)

• Future research ideas (34:55)

• Privacy-preserving reputation (37:33)

Additional resources:

• Spamming the Lightning Network

• Preventing Channel Jamming

• Bitcoin Optech: Channel jamming attacks

• The impacts of channel jamming

• Bitcoin problems: Channel balance probing

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Josibake joins us to talk about his work on the Bitcoin Core wallet, bitcoin data and onboarding to bitcoin development.

We discussed:

• Analyzing historical transaction data (1:25)

- Creating a publicly available dataset (4:12)

- What could it be used for? (7:30)

• Bitcoin Core wallet (9:00)

- Why have a wallet in Bitcoin Core? (10:00)

- Separation of GUI from wallet (12:35)

- Only use one input type when building transaction (13:40)

- PR #24584 in Bitcoin Core

- How is working on the wallet? (17:15)

• Cross-input signature aggregation (19:48)

- Catching up on history (20:40)

- Writing the BIP with Hackspec (22:05)

- Thoughts on shipping cross-input signature aggregation separately (22:50)

• Onboarding to Bitcoin development (28:35)

- Running the seminar with friends (29:55)

- Giving back to open source (31:20)

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Our topics:

• Lightning Dev Kit (1:04)

- Zeroconf Channels (2:22)

- Rapid Gossip Sync (3:46)

- How does LDK pick priorities? (8:55)

- LDK Lite (10:12)

- Will LSPs be needed forever? (12:25)

• Validated Lightning Signer (15:20)

- A Lightning Node's Problem with Hats

- VLS code base

• FROST and ROAST (23:00)

- Recovering a FROST wallet (24:00)

• Taproot adoption (26:18)

• Future of the Lightning Network (30:48)

• Stratum V2 (34:25)

- OFAC and mining (37:57)

- Other benefits over Stratum (39:59)

Thanks to Gurwinder Sahota for the sound engineering.

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We catch up with 0xB10C about monitoring pools and tracing code execution in nodes.

Our topics:

• What he's been up to since the residency (1:05)

• Monitoring the mempool (2:52)

• Mempool Observer

• Monitoring Mining pools (4:27)

• MiningPool Observer

• Mining pools not mining P2TR at Taproot activation (5:24)

• Why monitor the network? (8:20)

• Template discrepancies between pools and monitor (9:25)

• User-space Statically Defined Tracing (USDT) (11:07)

• Tracing Readme

• Using tracepoints to simulate coin selection (13:36)

• Why are tracepoints in production code? (14:38)

• Using tracepoints for P2P monitoring (17:05)

• Using tracepoints to review PRs (22:00)

• Benchmarking Erlay with USDT (22:42)

Other resources: - TransactionFee.info

Thanks to Emily Kee for the sound engineering.

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Gloria Zhao sits down with us to discuss her package relay proposal and what it is like as a relative newcomer to propose a big change.

• What's package relay? (1:04)

• Mailing List: Package Relay Proposal

• Why do people care about package relay? (3:12)

• What are these "contracting protocols" package relay matters for? (5:03)

• Pinning attacks (6:28)

• Why do you work on package relay? (6:55)

• What's special about the mempool? (10:18)

• How do you approach the security considerations? (12:07)

• Synthesizing information for the ones coming after you (15:27)

• What's next for package relay? (17:50)

• Bridging protocol development with L2 (20:55)

Additional resources:

• Mailing List: Package Mempool Accept and Package RBF

• Brink Podcast: Ep1 Mempool Policy

• Censorship and DoS Attacks: An intro to Mempool Policy

• Transaction Relay Policy for L2 Developers

• Mempool Garden

Thanks to Emily Kee for the sound engineering.

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Martin Zumsande joins us to tell us about the address spam in the summer of 2021 and his interests in AddrRelay and Bitcoin Core development.

We discuss with Martin:

• His background (1:38)

• Getting interested in Bitcoin (2:45)

• How to approach P2P (3:55)

• The network is changing (7:30)

• What's the purpose of the Address Manager (AddrMan)? (9:33)Peering differences to LN nodes (11:00)

• Ethan Heilman's talk on Network Partitioning Attacks (12:10)

• Addrman and eclipse attacks (12:27)

• AddrRelay and the role of node addresses (12:55)Getting connected to the network (13:37)

• Self-announcements (14:25)

• Address spam in summer 2021 and peer distribution (15:05)

• Correction: The peer would not get addresses-divided-by-peers addresses, but 2×addresses-divided-by-peers addresses as the addresses get forwarded to two peers each. (18:00)

• Estimating the Node Degree of Public Peers and Detecting Sybil Peers Based on Address Messages in the Bitcoin P2P Network by Matthias Grundmann (19:30)

• Simulating the network (20:15)

• Requesting addresses from peers (21:45)

• Walking through first connection of a node (25:25)Coinscope paper (27:10)

• Being a Bitcoin Core contributor (27:50)

Thanks to Emily Kee for the sound engineering.

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Postdoc Researcher Sergei joins Murch and Jonas to talk about channel balance probing in Lightning, privacy concerns in general, and the importance of researcher-developer collaboration.

We discuss:

• Sergei's background (1:50)

• Sergei's homepage with links to all prior research

• Lightning basics (2:50)

• Why LN payments fail (3:40)

• Why privacy is important (5:30)

• Privacy potential of Lightning vs L1 Bitcoin (6:40)

• How probing works (8:40)

• Why is balance discovery bad? (11:30)

• Persistent identities in Lightning (13:00)

• Multi-vector security model and trade-offs (17:45)

• "Twitter for your bank account" meme (20:20)

• The danger of overestimating Bitcoin's privacy (21:00)

• Lightning integrations and walled gardens (22:00)

• Lightning Service Providers and LN's centralized topology (23:05)

• LNBIG booth in El Salvador (25:30)

• Potential oligopoly of large nodes (27:15)

• Probing parallel channels (28:30)

• Analysis and Probing of Parallel Channels paper

• Combining probing with jamming (33:00)

• The limit on in-flight payments (36:00)

• StackExchange answer about transaction size limit

• Bad and good probing (41:20)

• Countermeasures and reputation (44:00)Overview of anti-jamming measures

• Hub-and-spoke terminology and aviation analogy (49:00)

• Doing research in Bitcoin and Lightning (53:10)

• Why Bitcoin is unique (55:10)

• Researcher-developer collaboration (58:00)

Related research:

• On the Difficulty... -- the first paper about LN balance probing

• An Empirical Analysis paper about three LN attack vectors including probing

• Counting Down Thunder paper about timing attacks

• Congestion Attacks paper about jamming

• Cross-layer Deanonymization paper about linking L1 and L2

• Flood & Loot paper about malicious fee negotiation strategies

• Hijacking Routes paper about adversarial fee undercutting

Thanks to Justin for the sound engineering.

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Postdoc Researcher Clara joins Murch to discuss their block building research. They cover their proposal, which outlines suggested improvements to the current Bitcoin Core block building algorithm using candidate sets.

Murch and Clara discuss:

• Building a valid block 101 (5:45)

• The current getblocktemplate algorithm (11:35)

• Child pays for parent (13:40)

• Is there something better? (15:45)

• How easy would it be to guess the next block? (27:25)

• Do we have a better idea than initially mining an empty block? (29:25)

• Empty blocks and SegWit (33:45)

• How to improve on the candidate set algorithm e.g., linear programming (35:00)

• Why should Bitcoin Core have better block building? (37:00)

• How to compare different block building techniques (38:55)

Thanks to Caralie for the sound engineering.

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Sanket describes to Murch his work on Miniscript. We explore uses for Miniscript, learn about intersections with PSBTs, Output Descriptors, and Taproot, and suss out the difference between Miniscript and Miniscript Policy.

Note: This episode was recorded in the context of travel for Bitcoin 2021. We apologize for the less polished than usual audio quality due to the different equipment and recording environment.

We discuss:

• What's Miniscript? (1:54)

• Partially Signed Bitcoin Transactions (PSBTs) (5:13)

• Analyzing PSBTs with Miniscript (7:22)

• How do Output Descriptors relate to Miniscript (10:16)

• Implementations of Miniscript (13:36)

• Semantic analysis of Scripts (14:54)

• Non-malleability of miniscript (22:47)

• Miniscript Policy (25:15)

• Rediscovering HTLCs (29:41)

• Miniscript uses (33:11)

• Removing script limitations with Taproot (34:42)

• Generic signing (35:53)

• Future work (37:34)

• The role of policy (40:24)

Related links:

• Miniscript website

• Rust Miniscript

• Miniscript C++ implementation

• Gramtropy

• miniscript on Libera Chat

Thanks to Caralie for the sound engineering, and thanks to Matthew Zipkin for assistance with squashing reverb artifacts.

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P2P experts Pieter and Amiti chat about the P2P network.

In this episode they cover:

• AddrRelay high-level goals and constraints (1:15)

• Very different than the goals of blocks and transactions

• Marginal fee rate (4:35)

• Should we consider different transport layers? (5:40)

• FIBRE Episode with Matt Corallo (7:40)

• The introduction of Addrman in 2012, PR #787 (8:55)

• What existed before AddrMan and the evolution of DoS resistance.

• Eclipse Attack paper (14:55)

• Sybil attack

• Addrman and eclipse attacks wiki page

• Anchors connections - PR #17428

• Connection exhaustion issue (19:50)

• Erlay (paper, BIP) (20:55)

• AddrRelay (23:15)

• Limiting addr black holes - PR #21528

• Rate limiting on address gossip in 22.0

• Leaky bucket rate limiter (27:00)

• Address Spam (29:20)

• Estimating the Node Degree of Public Peers and Detecting Sybil Peers Based on Address Messages in the Bitcoin P2P Network by Matthias Grundmann (31:35)

• Coinscope paper (31:45)

• TxProbe (32:00)

• Separate network stack (37:20)

• Fingerprint attacks (37:15)

• ASMAP (39:00)

Thanks to Caralie for the sound engineering.

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Amiti returns to the Chaincode office to discuss all things p2p.

We discuss:

• Why Amiti works on P2P (1:50)
• A framework for p2p design (4:25)
• How do we systemize Bitcoin Core knowledge? (6:20)
• Searchable #bitcoin-core IRC logs (8:35)
• Forward compatibility and upgradability (15:00)
• Partition resisitence (16:10)
• Eclipse Attacks (17:00)
• Altnet (20:40)
• Messages sent across the wire (20:55)
• AddrRelay and AddrMan (24:35)
• Bootstrapping, DNS seeds and address announcements (25:25)
  • DoS issues (27:35)
  • Address Manager (29:00)
  • New table and tried table (30:00)
• The Bitcoin network “dance” (31:25)
• Transaction download on Bitcoin’s p2p network comic (32:25)
• Addresses and proof of work (32:45)
• Inbound and outbound connections (34:00)
• Block relay only connections and full connections (35:35)

Thanks to Caralie for the sound engineering.

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In this Chaincode Decoded segment we talk about the fundamental role of Bitcoin's blockchain and some of its peculiarities.

We discuss:

• Purpose of the blockchain (0:40)

• Mining is a lottery, not a race (1:57)

• Why doesn't the same miner always win? (5:12)

• What happens if two blocks are found at the same height? (6:12)

• The longest reorgs (9:11)

• How does the blockchain work? (12:18)

• Headers-first synchronization and Ultraprune: Episode 1 with Pieter Wuille

• Episode 5: The UTXO set

• Why does Bitcoin converge on one chain? (15:20)

• Selfish mining paper: Majority is not Enough: Bitcoin Mining is Vulnerable

• Will we always find a new block? (18:04)

• Entropy sources in the block header

• Mining pools have disjoint hashing spaces (19:30)

• Correction: mining pools do not have a separate pay-out address for each participant, but give out a unique coinbase transaction stub for each.

• Eschaton block

Thanks to Caralie for the sound engineering.

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In Episode 13, we sit down again with Matt Corallo and discuss his work on the Lightning Development Kit (LDK).

In this conversation we cover:

• Starting Rust-Lightning (1:20)

• Language bindings challenges (4:09)

• FFI (5:32)

• Interoperability of Lightning (7:10)

• Zero-value invoices (7:35)

• Keysend/push payments/spontaneous payments (8:20)

• What is the LDK stack? (9:29)

• Anchor Outputs (10:41)

• Child pays for parent (CPFP) (11:02)

• Who tracks the onchain state when using LND? (12:30)

• LDK tracks the channel commitment transaction, how is that done? (13:45)

• Compact block filters

• Contrasting multiple implementations working from a spec in Lighting vs. no spec with one dominant reference implementation in Bitcoin (14:58)

• The Lightning Spec

• What's the state of the Lightning Network? Have we moved beyond #reckless? (18:49)

• Denial of Service (DoS) vulnerabilities

• Channel Jamming (22:00)

• Eltoo and the punishment dynamic (22:45)

• Will the network trend to trusted relationships and lend itself to KYC? (24:50)

• FATF updates its guidance on Virtual Asset Service Provider (VASP) (26:50)

• Where LDK goes from here? (29:55)

Thanks to Caralie for the sound engineering.

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The Chaincode Decoded segment returns and we jump into the deep end of the mempool.

• Child Pays for Parent (CPFP) (2:15)
• How miner evaluate fee rates (4:34)
• Why is it hard to estimate fee rates? (6:03)
• How do exchanges estimate fees? (8:00)
• Will the mempool empty again? (9:23)
• Miner/pools and the need for a high fee environment (11:04)

• Replace by Fee (RBF) (14:05)

• BIP 125

• Mempool eviction and the problems it can cause (19:04)
• Anchor Outputs (20:50)
• Package Relay (21:06)

• Ways to use the blockspace more efficiently (22:15)

• blockchain.com implements Segwit

Thanks to Caralie for the sound engineering.

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This revisits a segment we call Chaincode Decoded. In this episode, we'll learn how to say Bech32 and also what it and Bech32m are. Enjoy!

Correction: The characters removed from the set are 1 B I O (2:20)

• Why do we need Bech32? (0:57)
• What is the distinction between Bech32 and native SegWit? (3:20)
• Why does Taproot need a new address format? (4:13)

• Bech32 length extension mutation weakness (11:20)

• mailing list post

• Bech32m (12:25)

• BIP350

Further resources:

• Pieter Wuille: New Address Type for SegWit Addresses (presentation)
• Sipa demo
• Bech32 adoption
• (Some of) the math behind Bech32 addresses

Thanks to Caralie for the sound engineering.

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In part 2 of this sit down with Carl Dong, Murch and Jonas cover the delicate work of modularizing the Bitcoin consensus engine.

In this conversation, we cover:

• Carl's De-globalize ChainstateManager PR (2:25)

• Async Block Processing PR

• Deglobalize class of chainstate manager (g_chainman) (3:40)

• AssumeUTXO

• global variables and main (5:25)

• scripted diff (9:35)

• 0.8 upgrade consensus failure (11:25)

• Jorge Timon's libconsensus project (13:10)

• current libbitcoinconsensus only does script verification (13:25)

• the case for multiple implementations (14:40)

• ABI (15:10)

Thanks as always to Matthew Zipkin for the sound engineering.

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In part 1 of this sit down with Carl Dong, Murch and Jonas get into the weeds of all things build system. Stay tuned for the second half of this conversation when Carl describes his recent adventures isolating the libconsensus engine.

In this conversation, we cover:

• GUIX (2:25)

• talk at 2019 Breaking Bitcoin about reproducible builds

• Gitian builds (4:15)

• Fake time (4:50)

• Timestamps and reproducibility of packages (6:33)

• reproducible-builds.org (6:57)

• SOURCE_DATE_EPOCH

• Toolchains (14:40)

• Windows Builds and reproducibility (15:20)

• GCC libtool pointer confusion

• NSIS (20:25)

• Using Debian as an example (22:56)

• User choice in their security model (28:15)

• Making the process accessible (31:20)

• Mac OS X Toolchain & SDK and cross-compiling (33:30)

Thanks as always to Matthew Zipkin for the sound engineering.

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After a long hiatus, we return to talk with new Chaincode member Murch and get his take on enterprise wallets and UTXO management.

In this conversation, we cover:

• Enterprise UTXO management (3:35)

• The impact of the 2017 hype cycle (4:30)

• The importance of UTXO set minimization (5:30)

• The fee market today (6:44)

• Batching Transactions (9:15)

• Payment Batching

• Consolidations (11:05)

• Consolidation of 4 Million UTXOs at Xapo

• Change splitting (14:10)

• Replace By Fee (16:04)

• RBF in the wild

• Fee bumping

• SegWit (21:10)

• How enterprises estimate fees (25:00)

• Omnibus wallets (28:05)

• Off-chain sending (31:50)

• Taproot (33:57)

Other resources: - Bitcoin Optech Field Report: How segwit and batching could have saved half a billion dollars in fees

Thanks as always to Matthew Zipkin for the sound engineering.

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In Episode 7, we chat with Nadav Kohen of Suredbits and discuss payment points as an alternative to HTLCs on the Lightning Network.

In this conversation we cover:

• Payment points (1:55)

• Blog post part 1

• HTLCs (2:00)

• Timelocks (4:16)

• HTLC drawbacks (5:38)

• Payment decorrelation

• Wormhole attack presented in Anonymous Multi-Hop Locks for Blockchain Scalability and Interoperability (6:35)

• Point time lock contracts (PTLCs) (9:50)

• Adaptor signatures on Schnorr

• Proof of payment (13:25)
• Invoiceless transactions (15:05)
• Hashes, pre-images, and HTLC mechanics (16:35)
• Onion analogy (18:55)
• PTLC mechanics (19:30)
• Why don’t we use PTLCs today? (22:15)
• Lightning in Scriptless Scripts posting by Andrew Poelstra March 2017
• Improving proof of payment (26:10)
• Stuckless payments (30:46)
• Spam on Lightning (35:46)
• Selling Signatures and Schnorr signatures off the main chain (36:55)
• Contingent payments (39:20)
• Escrow contracts (41:28)
• Atomic multiparty setup and payment renegotiation (46:02)
• ETA of payment points (48:02)

Thanks as always to Matthew Zipkin for the sound engineering.

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In Episode 6, we sit down with Matt Corallo and discuss his work on compact blocks and the FIBRE network.

In this conversation we cover:

• Selfish mining (2:03)

• Majority is not Enough: Bitcoin Mining is Vulnerable

• Optimal Selfish Mining Strategies in Bitcoin

• Ethereum's larger pools making superlinear profits (5:10)
• Defining selfish mining (9:52)

• Compact blocks (12:37)

• FAQ

• BIP152

• Reference implementation

• FIBRE (20:28)

• Forward error correction (24:14)

• Shamir secret sharing

• Difference between TCP and UDP (29:21)

Thanks as always to Matthew Zipkin for the sound engineering.

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This is our first Chaincode Decoded Podcast. In this new podcast format, we'll dive into the details of a concept we've talked about on previous shows. No guests, no news, just Jonas and John talking about Bitcoin. A podcast by Bitcoin nerds for Bitcoin nerds.

In the first episode, we talk about the UTXO set. We'd love to know what you think!

Ultraprune - episode 1 (1:20)

Assume UTXO - episode 4 (1:28)

The cache layer (8:02)

Dbcache parameter (9:48)

- John talks about latency comparisons on a human scale. (Note: He incorrectly says that 1 second for RAM access equates to "months or years" for disk access. Actually 4 minutes for RAM access equates to 1-9 months for disk access.)

Different ideas on how to keep track of the UTXO set (11:29)

- utreexo (13:48)

What’s the future of the size of the UTXO set? (13:54)

UTXO consolidation (15:02)

UTXO selection (16:48)

• Murch’s thesis on coin selection
• Branch and bound

H/T to Amiti for the idea of the format. Thanks as always to Matthew Zipkin for the sound engineering.

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Next in the studio, we caught James O'Beirne, who until recently was a co-worker of ours at Chaincode. We talked to James about his experience at the Chaincode residency, his most recent project Assume UTXO (GitHub issue, proposal, talk) and how he champions and effects change in Bitcoin Core.

Discussed in this episode:

• 2018 residency (2:42)

• Choosing what to work on (5:40)

• Fork detection framework (6:55)

• Initial block download (IBD) (8:10)

• What a node does during IBD 1110

• DNS seeds (11:30)

• UTXO set (12:30)

• Parallelized signature validation (14:20)

• Assume valid (14:40)

• Different than checkpoints (17:30)

• Updating assume valid value in the code (0.19, 0.18) (19:00)

• Assume UTXO (21:20)

• Platform and memory considerations (27:15)

• Criticisms (27:55)

• Championing a big change in Bitcoin Core (32:20)

If you like this, find more shows at podcast.chaincode.com. Thank you to Matthew Zipkin for sound engineering.

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For our third episode, we talked to Jeremy Rubin about his recent CHECKTEMPLATEVERIFY proposal. During our discussion, we touch on the history of covenant proposals, vaults, payment pools, CTV's synergies with Taproot and more.

Notes:

• What is CHECKTEMPLATEVERIFY (CTV)? (4:30)

• What is a covenant? (5:25)

• CoinCovenants using SCIP signatures, an amusingly bad idea (2013) (7:15)

• Bitcoin Covenants AKA MES16 paper (2016) (8:15)

• Talk at Stanford Blockchain Conference (2017) (9:20)

• Why covenants? (11:43)
• Utxos.org

• Vaults (12:10)

• Annuity type vaults (13:40)

• Payment pools (18:00)
• Synergies with Taproot (22:11)
• SIGHASH_NOINPUT/ SIGHASH_ANYPREVOUT (24:31)
• CTV and lightning channels (26:30)
• Congestion control (32:04)
• CreateNewBlock() (33:09)

If you like this, find more shows at podcast.chaincode.com. Thank you to Matthew Zipkin for sound engineering.

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For our second episode, we pick up where we left off with Pieter Wuille in episode 1. If you missed that one, you should go back and listen to it first.

Pieter has been a Bitcoin protocol developer and contributor to Bitcoin Core since 2011. In that time, he’s authored or contributed to some of the most important developments, including segwit, bech32, libsecp, HD wallets, schnorr and taproot, and many others.

We talked to Pieter about his thoughts on the lessons learned from the March 2013 Consensus Fork as well as libsecp and Pieter’s thoughts about Bitcoin in 2020.

Discussed in this episode:

• Lessons learned from the 0.8 consensus failure (1:00)
• BIP66 - Strict DER signatures (3:13)
• Satoshi’s usage of OpenSSL (3:47)
• OpenSSL and DER encoding (5:35)
• libsecp256k1 (12:12)
• Hal Finney’s post on the special properties of the secp256k1 (12:50)
• Peter Dettman and Bouncy Castle (16:58)
• Imagining P2SH from the beginning (26:20)

If you like this, find more shows at podcast.chaincode.com. Thank you to Matthew Zipkin for sound engineering.

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For our first episode, we talked to Bitcoin Core contributor Pieter Wuille.

Pieter has been a Bitcoin protocol developer and contributor to Bitcoin Core since 2011. In that time, he’s authored or contributed to some of the most important developments, including segwit, bech32, libsecp, HD wallets, schnorr and taproot, and many others.

We talked to Pieter about his thoughts on some of those influential PRs, including headers-first syncing and ultraprune, and hear about the motivation for those changes and how he thinks about them now. This is a two-parter and in the next episode, we’ll hear about libsecp and Pieter’s thoughts about Bitcoin in 2020.

Discussed in this episode: * Headers-first syncing (3:30) * Tracking peer state and finding good peers (13:00) * How Bitcoin Core development culture has changed in the last 9 years (18:11) * Bitcoin test evolution (19:00) * Ultraprune (21:55) * March 2013 Consensus Fork (26:50):

• March 2013 Chain Fork Post-Mortem

• Analyzing the 2013 Bitcoin fork

If you like this, find more shows at podcast.chaincode.com. Thank you to Matthew Zipkin for sound engineering.