Hello everyone, I am thrilled to announce the public release of Penlock!
The goal is achieved! If you have a printer, scissors, a craft knife, and a pin, you can mechanically secret-split a 12-word seed phrase in under two hours. This includes the entire process—learning, printing, assembling, executing, and storing the shares. Penlock is a printable paper calculator that guides you through splitting a seed phrase into a 2-of-3 backup. It is open-source, uses straightforward and robust cryptography, and includes various fail-safes that protect against errors. A beta was announced on this list last year, and the public release is now available at: <https://v1.penlock.io/en/> This release breaks backward-compatibility with the beta, allowing for enhancements that make Penlock significantly easier to operate. Here are the main improvements in v1: - Faster Secret-Splitting: Penlock now focuses exclusively on producing 2-of-3 backups using its own paper-optimized splitting algorithm. The previous iteration supported K-of-M splitting with Shamir Secret Sharing, but at the cost of more complexity and a clunkier 2-of-3 process. Since 2-of-3 covers nearly all use cases, optimizing for it seemed like the right approach. - Backup Strategy Template: Penlock now suggests a generic, adaptable backup strategy that helps set up offsite recovery and trust-minimized inheritance. In short, each share is tied to a different type of storage: Digital, Social, and (optionally) Legal. This ensures an attacker would have to run two different types of attacks, and makes it hard for a party holding one share to obtain a second one. You can find more details at <https://v1.penlock.io/en/split#strategy>. - On-Paper Error Correction: Penlock v1 introduces what I believe to be the first on-paper error correction algorithm. Each BIP39 word is extended with two pre-computed parity symbols, guaranteeing per-word unambiguous correction of 1 error and detection of 2. In practice, it's also possible to fix a word with two errors, though it requires a little bit of patience. - Easier Seed Phrase Generation: Penlock also offers BIP39 seed phrase generation as an extra feature. The whole process has been redesigned into one of the simplest ways to generate a seed phrase by hand. Penlock was inspired by Codex32 from Andrew Poelstra and Russell O'Connor. It's been a two-year quest to adapt their concept for BIP39 seed phrases, iterating toward the best UX I could craft without compromising security. These improvements often required breaking compatibility with previous versions, which made me reluctant to propose a public version until the design stabilized into something final. I believe I have finally reached the best formula I can think of, hence this release. The feedback so far has been very positive, and I hope you find it interesting too! Please share any feedback or questions, and let me know what you think! Best, Rama Gan P.S.: Penlock's wheel also happens to be an interesting cryptographic puzzle—can you reverse-engineer Penlock's secret splitting algorithm just by looking at it? -- You received this message because you are subscribed to the Google Groups "Bitcoin Development Mailing List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/d/msgid/bitcoindev/GbNAPQX2Q4TzZvS6aWLPf3iy7z1yTXVrgnPpXazBjdcWH-zROBEBieE02r6GX128LM7mml6oTzAmlboV97EWpG1ujLcVZ6fx6uihUMXxCEo%3D%40proton.me.
