Jonas Nick details Shrimps, a post-quantum hash-based signature scheme where signatures are 350 bytes on a primary stateful device. If that device is lost, imported devices produce 2.5 kilobyte signatures, with a final 8 kilobyte fallback for catastrophic failure.
Shrimps and its predecessor Shrinks require wallets to be stateful, tracking an incrementing integer for each public key to count signatures. If this state is lost or corrupted, security breaks and the wallet must use a large fallback signature.
Conduition highlights isogeny-based cryptography as a promising post-quantum candidate because its structure allows key re-randomization. This enables BIP32-like hierarchical key derivation and Taproot-like key tweaking, features hash-based and lattice-based schemes struggle to replicate.
SkiSign, an isogeny-based signature scheme, has 65-byte public keys and 148-byte signatures. Verification is about 50 times slower than Schnorr or Dilithium, posing a potential bottleneck for full block validation.
Conduition notes isogeny cryptography relies on the supersingular isogeny path problem, a newer but well-studied assumption. He cautions that schemes like SkiSign and PRISM have complementary security proofs, making it hard to prove both secure simultaneously.
Armin describes how wallet fingerprints - artifacts like signature grinding, SIGHASH flags, and nSequence values - can break PayJoin privacy. Analysts can partition transaction inputs between sender and receiver by spotting inconsistent behaviors between collaborating wallets.
Explicitly stating SIGHASH_ALL in Taproot signatures is a wasteful bug that creates a fingerprint. Since Taproot defaults to SIGHASH_ALL, including the byte adds unnecessary transaction weight and identifies non-compliant wallets.
BIPs 440 and 441, part of the "script restoration" effort, are now published. BIP 440 proposes a VAR Ops budget for limiting script complexity, while BIP 441 proposes re-enabling disabled opcodes like OP_CAT within a new Tapscript version.
Pais proposes BIP 2130, a standard for wallet backup metadata formats. It aims to create an interoperable way to export and import not just descriptors, but full wallet state including labels, transaction history, and coin data.
Eclair 3269 adds automatic liquidity reclamation, closing idle redundant channels. It reduces relay fees over time and closes a channel if, after five days at minimum fee, payment volume stays below 5% of capacity and the local balance is over 25%.
LDK adds support for zero-channel-reserve channels, primarily for LSP-user relationships. This lets users commit their full on-chain balance to a channel, shifting the trust and risk onto the service provider.
LND implements proper MuSig2 nonce handling and RBF support for cooperatively closing simple Taproot channels. The update hardens the protocol against nonce reuse, which could expose private keys.