Published on: 2019-02-07T02:42:55+00:00
A discussion on the bitcoin-dev mailing list focused on using shuffled decks of cards as a physical backup for private keys. Devrandom suggested using 50+ 6-sided dice rolls to obtain around 128 bits of entropy, while Alan Evans pointed out that simply using SHA512 was not enough and highlighted a condition where the master key would be invalid if IL is 0 or ≥n. Evans also suggested creating a scheme that takes Cards -> Entropy so that both BIP39 and non-BIP39 fans can generate and store their root xprv.Prior art was mentioned in Ian Coleman's BIP39 site, which already supports cards and dice and can calculate the Total Bits of Entropy. The site can handle card replacement and multiple decks, addressing some of the concerns raised in the discussion. Additionally, James MacWhyte suggested drawing a diagonal line on the side of the deck from corner to corner to ensure the order of the shuffled deck remains intact.In summary, the discussion highlighted the limitations of using SHA512 alone for generating a secure master key and suggested a scheme that takes cards and generates entropy. Ian Coleman's BIP39 site was referenced as an example that supports this approach. A suggestion was made to use 50+ 6-sided dice rolls for additional entropy. Finally, a tip was provided on how to prevent the order of shuffled cards from being mixed up by drawing a diagonal line on the side of the deck.
Updated on: 2023-08-02T00:27:07.431926+00:00