Weekly technical newsletter about Bitcoin and Lightning development, written for engineers.
17 publications
Work has resumed on a specification and experimental Bitcoin Core support for TCP hole punching, which could help home nodes behind routers accept peer connections. A draft BIP also proposes shared spending-policy formats for co-signers used to emulate covenants.
Bitcoin Optech
Greg Sanders, Antoine Poinsot, Elias Rohrer, Oleksandr Kurbatov and Nishant Bansal join the Optech hosts for the #429 recap, which starts with Bitcoin Core #36665, #36667 and #36669 before moving to the updated security policy. Multiparty silent payments, a Core Lightning DoS disclosure and Eclair 0.14.6 come later; the transcript is still pending.
Bitcoin Optech
A channel announcement naming the same node at both ends could crash Core Lightning 25.02 through 26.04 on every restart, at a cost to the attacker of only onchain fees; the fix landed in 26.04.1. Newsletter #429 pairs that disclosure with Oleksandr Kurbatov's protocol for multiparty silent payment inputs and Bitcoin Core's faster point releases for easily discoverable bugs.
Bitcoin Optech
Adam Gibson walks through Lichen, his single-issuer layer 2 with unilateral exits validated by BitVM, on the #428 recap. João Dias and Vincenzo Palazzo are the other guests of Gustavo Flores Echaiz and Brandon Black; descriptor syntax for hash preimages, rbitcoin 0.8.0 and LND v0.21.5-beta.rc1 also come up.
Bitcoin Optech
Lichen, a design from Adam Gibson, lets users of a single-issuer layer 2 redeem bitcoin onchain when the hub refuses or goes offline, with disputes settled through Groth16 proofs and presigned BitVMX transactions. A second item in Newsletter #428 covers João Dias's proposal for a private preimage form of miniscript hash fragments; Ibis Wallet v5.0-beta and rbitcoin 0.8.0 appear among software updates.
Bitcoin Optech
Erick Cestari explains two Eclair memory bugs in the channel-opening handshake on the #427 recap, one caught by Matt Morehouse's fuzzer and the other with an LLM. Adam Gibson then presents LN-GAP, whose example is a chess game played inside a Lightning channel. Bitcoin Core 32.0rc4 and a batch of Eclair fixes come later in the show.
Bitcoin Optech
Eclair v0.14.0 and earlier could be run out of memory during channel opening: one bug leaked about 1 MB per second, and another exhausted 4 GB in about 48 minutes over a single connection with no onchain cost. Both were fixed in v0.14.1. Newsletter #427 sets them beside LN-GAP, Adam Gibson's scheme for multi-round contracts inside Lightning channels, which rests on an honest-majority committee.
Bitcoin Optech
Clara Shikhelman opens the #426 recap with Shielded Bitcoin, a proposal she co-authored to move bitcoin without broadcasting sender, receiver or amounts, and without consensus changes or operators. Elias Rohrer of Spiral then takes the LDK v0.3-rc3 and v0.2.7 releases along with LDK code changes, with Gustavo Flores Echaiz hosting.
Bitcoin Optech
Shielded Bitcoin, proposed by Misha Komarov with Clara Shikhelman and Aleksei Moskvin, is a metaprotocol for private onchain transfers that needs no consensus change, though it requires a one-time setup ceremony and leaves a trace on entry and exit. Anthony Towns drafts a BIP letting peers pick their own one-byte message IDs over BIP324 transport, and Fabian Jahr asks whether tagged hash tags should carry BIP numbers.
Bitcoin Optech
Eclair's feature-bit parser allocated over 300 MB while handling a single maximum-length message, Matt Morehouse says on the #425 recap, and the fix cut that to roughly 200 KB. Gustavo Flores Echaiz and Brandon Black go on to wallet label synchronization, PQC output types, BIP54 time warp bounds and covenant proposals for vaults.
Bitcoin Optech
A 64 kB gossip query could inflate to 64 MB in Eclair v0.13.1 and earlier, and a maximum-length init message churned through about 300 MB; Matt Morehouse disclosed both DoS bugs, fixed in v0.14.0. Jakub is gauging interest in syncing BIP329 wallet labels through an untrusted store, while Newsletter #425's consensus section returns to post-quantum output types.
Bitcoin Optech
Ahmet Kurt explains PQLN, post-quantum security for Lightning's offchain surfaces, in the first pre-recorded segment on Optech's show. Jan B, a Bitcoin Core contributor who reviews PRs and works on kernel code, joins Gustavo Flores Echaiz and Mike Schmidt for the live part, where Bitcoin Core 32.0rc2 and its testing guide are on the agenda.
Bitcoin Optech
PQLN, from Ahmet Kurt and collaborators, makes Lightning's gossip, transport, invoices, offers and onion quantum-secure but leaves onchain operations alone, since those would need a consensus change. Bandwidth is the price: a node downloads 10 times and stores 9 times as much data, while ML-DSA signing takes just 0.33 ms. A working rust-lightning implementation can be tested now.
Bitcoin Optech
Utreexo's accumulator takes less than 1 kB where a node otherwise keeps a UTXO set of roughly 11 GB, Davidson Souza explains on the #423 recap, at the cost of more bandwidth. Eric Price of MARA and PortlandHODL are also guests, with vardiff controllers that strand slowing miners and a draft BIP for unspendable internal keys on the list.
Bitcoin Optech
Mining pools can strand a slowing miner on a share difficulty set for its old speed, Eric Price argues on Delving Bitcoin; his remedy is a timer that lowers difficulty after an interval with no shares. Davidson Souza wants the SwiftSync hintsfile to remove Utreexo deletion proofs during initial block download, and NTL has drafted a BIP for unspendable taproot internal keys.
Bitcoin Optech
Adam Gibson walks Optech hosts Mark Erhardt and Mike Schmidt through Babilonia, his coinjoin protocol disguised as covert bets, and points to a 1997 Ron Rivest paper on lottery-style micropayments as an older root of probabilistic payments. Rob Segers then discusses his silent payments light client measurements.
Bitcoin Optech
Babilonia, a proposal from Adam Gibson, dresses coinjoins up as onchain coin flips that look like normal payments from outside, though his paper admits the protocol's efficacy has no clear measure yet. Rob Segers' benchmarks put BlindBit Oracle v2 at about 2.1x the download of a taproot-only filter plus tweak data, in exchange for no false positives. LDK v0.2.6 patches a denial-of-service vulnerability.
Bitcoin Optech
