Episode 101: The COLDCARD Hack

Aaron and Sjors discuss Bitcoin Core 32.1 and its updated security disclosure policy in this live conference recording, followed by audience questions. Links Bitcoin Core 32.1 release announcement and release notes Bitcoin Core security disclosure policy Pull requests and discussion Tor proof-of-work defenses: #33414 CJDNS support: discussion #36041 and release-note update #36202 Replacing libevent with a custom HTTP server: #35182 More inbound block-relay capacity: #28463 Fetching block inputs in parallel: #35295 Removing the experimental warning from send and sendall: #35601 Watch-only wallet exports: RPC #32489 and GUI #872 Undo-file overflow: advisory and fix #36669 TCP urgent-data memory exhaustion: advisory and fix #36665 The briefly mentioned paused-peer memory issue: advisory and fix #36667 Chapters 00:00:00 Live introduction 00:05:00 Tor proof-of-work defenses and CJDNS 00:12:06 Removing libevent: dependencies and the RPC server 00:15:40 More inbound block-relay connections 00:19:16 Faster validation with parallel input fetching 00:25:16 Wallet RPCs and watch-only exports 00:28:59 AI and the security disclosure policy 00:34:19 Undo-file overflow and chain reorganizations 00:41:15 TCP urgent data and memory exhaustion 00:48:11 Audience Q&A: watch-only wallets and descriptors Aaron’s Nostr: npub1art8cs66ffvnqns5zs5qa9fwlctmusj5lj38j94lv0ulw0j54wjqhpm0w5 Sjors’ Nostr: npub1v25jqj332n630klwtqeqxgyrjl4alw4phmluhu2x6lcxzwy9m03suqexw3 If you’d like to sponsor the show, please email info at bitcoinexplainedpodcast.com. https://bitcoinexplainedpodcast.com/

Aaron and Sjors discuss the COLDCARD hack: the bug itself, how it could have happened, and some reflections on having had Coinkite as a sponsor. Note: If you’re using a COLDCARD and still haven’t moved your funds to a secure location, do this as soon as possible. (Also listen to the previous emergency broadcast.) Further reading: https://wizardsardine.com/blog/coldcard-rng-vulnerability/ https://engineering.block.xyz/blog/predictable-rng-fallback-and-32-bit-reseed-in-coldcard-firmware Chapters 00:00:00 The Hack and Weak Seeds 00:05:33 Simulator Code and Weak Randomness 00:19:15 Why MK4 Was Vulnerable 00:25:56 Open Source and Security Audits 00:35:34 Preventing the Next Failure 00:38:47 Multisig and Custody Tradeoffs 00:44:11 Could Victims Recover Funds? 00:48:50 Our Sponsorship Responsibilities Aaron’s Nostr: npub1art8cs66ffvnqns5zs5qa9fwlctmusj5lj38j94lv0ulw0j54wjqhpm0w5⁠ Sjors’ Nostr: npub1v25jqj332n630klwtqeqxgyrjl4alw4phmluhu2x6lcxzwy9m03suqexw3 If you’d like to sponsor the show, please email info at bitcoinexplainedpodcast.com. https://bitcoinexplainedpodcast.com/

The COLDCARD hardware wallet has a critical vulnerability. If you are using the COLDCARD to store bitcoin, move them to a secure location as soon as you can. More information: https://blog.coinkite.com/coldcard-mk3-seed-generation-warning/ https://blog.coinkite.com/entropy-technical-backgrounder/

Aaron and Sjors discuss what’s new in Bitcoin Core 31. Chapters 00:00:00 Episode 100 and Core 31 00:02:41 Cluster Mempool 00:10:45 Package Relay and Fee Selection 00:18:59 Private Broadcast over Tor 00:24:03 ASMAP and Eclipse Attacks 00:31:45 The Private Broadcast Bug 00:33:44 Mining IPC and Stratum V2 This episode’s sponsor: CoinKite, maker of the COLDCARD. Aaron’s Nostr: ⁠npub1art8cs66ffvnqns5zs5qa9fwlctmusj5lj38j94lv0ulw0j54wjqhpm0w5⁠ Sjors’ Nostr: npub1v25jqj332n630klwtqeqxgyrjl4alw4phmluhu2x6lcxzwy9m03suqexw3

Aaron and Sjors discuss what’s new in Bitcoin Core 30. Chapters 00:00:00 Release Overview and Controversy 00:04:58 OP_RETURN Policy Changes 00:12:32 Lower Minimum Relay Fees 00:23:06 Sigops Limits and Consensus Cleanup 00:31:42 Package Relay and Orphanage 00:37:04 The New bitcoin Command 00:38:48 Mining IPC and Stratum V2 00:44:55 Automatic Port Forwarding This episode’s sponsor: CoinKite, maker of the COLDCARD. Aaron’s Nostr: ⁠npub1art8cs66ffvnqns5zs5qa9fwlctmusj5lj38j94lv0ulw0j54wjqhpm0w5⁠ Sjors’ Nostr: npub1v25jqj332n630klwtqeqxgyrjl4alw4phmluhu2x6lcxzwy9m03suqexw3

Aaron and Sjors discuss the proposal to remove the OP_RETURN limit from Bitcoin Core. Chapters 00:00:00 Opening and COLDCARD sponsor 00:03:57 The OP_RETURN debate and how the opcode works 00:13:35 Fake public keys and UTXO set pollution 00:19:37 Relay policy, consensus and the 80-byte limit 00:28:50 New metaprotocols, inscriptions and data costs 00:38:07 Citrea and the case for lifting the limit 00:42:59 Can relay filters stop blockchain spam? 00:52:45 Mining centralization, fee estimates and compact blocks 00:59:52 Fighting spam with consensus changes 01:04:28 Configurable limits and the harm reduction debate This episode’s sponsor: CoinKite, maker of the COLDCARD. Aaron’s Nostr: ⁠npub1art8cs66ffvnqns5zs5qa9fwlctmusj5lj38j94lv0ulw0j54wjqhpm0w5⁠ Sjors’ Nostr: npub1v25jqj332n630klwtqeqxgyrjl4alw4phmluhu2x6lcxzwy9m03suqexw3

Aaron and Sjors discuss what’s new in Bitcoin Core 29. Chapters 00:00:00 Bitcoin Core 29: introduction 00:01:39 Sponsor: Coinkite and COLDCARD Q 00:02:52 Replacing UPnP with PCP for inbound connections 00:12:16 Ephemeral dust and Lightning channel fees 00:22:43 Block reserved weight for mining templates 00:27:31 Time warp protection and mining timestamps 00:42:09 Full RBF becomes the only policy 00:43:50 Building Bitcoin Core with CMake 00:45:22 Exporting the UTXO set to SQLite === This episode’s sponsor: CoinKite, maker of the COLDCARD. Aaron’s Nostr: ⁠npub1art8cs66ffvnqns5zs5qa9fwlctmusj5lj38j94lv0ulw0j54wjqhpm0w5⁠ Sjors’ Nostr: npub1v25jqj332n630klwtqeqxgyrjl4alw4phmluhu2x6lcxzwy9m03suqexw3

In Bitcoin, Explained 96, Aaron and Sjors discuss some recent innovations in mining, and in particular mining decentralization. Specifically, they discuss the Stratum V2 and DATUM mining protocols to decentralize transaction selection in mining pools, the open source hardware Bitaxe miner, and some recent proposals to make decentralized mining pools like P2Pool more viable. Chapters 00:00:00 Introduction and mining decentralization 00:06:48 Why mining centralization threatens censorship resistance 00:11:10 Stratum V2: miners choose transactions 00:14:18 DATUM and the limits of pool decentralization 00:20:14 Why predictable payouts favor large pools 00:23:26 Bitaxe: open source hobby mining 00:30:46 P2Pool: mining without a central operator 00:35:14 Reviving P2Pool: latency and payout challenges 00:39:13 Lightning swaps and ecash for mining payouts === This episode’s sponsor: CoinKite, maker of the COLDCARD. Aaron’s Nostr: ⁠npub1art8cs66ffvnqns5zs5qa9fwlctmusj5lj38j94lv0ulw0j54wjqhpm0w5⁠ Sjors’ Nostr: npub1v25jqj332n630klwtqeqxgyrjl4alw4phmluhu2x6lcxzwy9m03suqexw3

In Bitcoin, Explained 95, Aaron and Sjors discuss the new Bitcoin Core 28.0 release. Specifically, they cover upgrades to Bitcoin’s testnet (testnet 4), new mempool policies, full RBF integration, the introduction of assume UTXO, improved wallet migration support and the implementation of block file XOR. https://bitcoincore.org/en/download/ Release notes: ⁠https://bitcoincore.org/en/releases/28.0/⁠ Chapters 00:00:00 Introduction and Coinkite sponsor 00:04:21 Bitcoin Core 28 and Testnet 4 00:12:04 Mempool fees and Lightning channel closes 00:17:53 One-parent, one-child package relay 00:23:27 V3 transactions and TRUC policy 00:27:18 Pay-to-anchor outputs for fee bumping 00:30:19 Full RBF becomes the default 00:33:59 AssumeUTXO on mainnet 00:36:55 Migrating legacy wallets to descriptors 00:39:28 Block file XOR and antivirus protection This episode’s sponsor: CoinKite, maker of the COLDCARD. Aaron’s Nostr: ⁠npub1art8cs66ffvnqns5zs5qa9fwlctmusj5lj38j94lv0ulw0j54wjqhpm0w5⁠ Sjors’ Nostr: npub1v25jqj332n630klwtqeqxgyrjl4alw4phmluhu2x6lcxzwy9m03suqexw3

In this episode of Bitcoin, Explained, Aaron and Sjors welcome Ruben Somsen and Josie to the show to discuss BIP 352, their now-finalized Bitcoin Improvement Proposal for Silent Payments. As previously discussed in episode 58, Silent Payments use a special type of addresses that allow senders to generate public keys for transaction recipients, in such a way that these recipients can in turn generate the associated private keys. This benefits privacy, as Bitcoin users can freely share a static address, without this resulting in address reuse on the Bitcoin blockchain. Aaron, Sjors, Ruben and Josie recap how this works. and discuss some of the implementation details for the BIP, including how light clients can utilize Silent Payments, how these payments are made compatible with CoinJoin, and an extra feature called “labels”. Chapters 00:00:00 Welcome, guests and CoinKite sponsor 00:01:21 BIP 352: from proposal to implementation 00:06:46 How silent payments protect address privacy 00:09:00 Shared secrets, scan keys and spend keys 00:18:11 Scanning the blockchain for incoming payments 00:22:46 Private light clients, indexing and compact filters 00:35:23 The Hotel California problem: expiry and revocation 00:39:30 CoinJoin, hardware wallets and verifiable shared secrets 00:48:02 Labels: identifying payments without extra scanning 00:55:37 Wallet adoption and implementation roadmap === This episode’s sponsor: CoinKite, maker of the ColdCard. Aaron’s Twitter: @AaronvanW Aaron’s Nostr: npub1art8cs66ffvnqns5zs5qa9fwlctmusj5lj38j94lv0ulw0j54wjqhpm0w5 Sjors’ Twitter: @provoost Sjors’ Nostr: npub1v25jqj332n630klwtqeqxgyrjl4alw4phmluhu2x6lcxzwy9m03suqexw3 Ruben’s Twitter: @SomsenRuben Josie’s Twitter: @josibake If you’d like to sponsor the show, please email info at bitcoinexplainedpodcast.com. https://bitcoinexplainedpodcast.com/