BIP85 support - Deterministic Entropy From BIP32 Keychains

[AndreasGassmann]

There is a new BIP that is slowly being adopted by hardware wallets. Coldcard was the first to add support a couple months ago, now others are starting to plan this as well.

A non-technical explanation of BIP85 is that it allows you to deterministically generate new mnemonics out of a mnemonic.

So for example, you can have a mnemonic:

install scatter logic circle pencil average fall shoe quantum disease suspect usage

And then generate another mnemonics out of it, eg:

Index 1: girl mad pet galaxy egg matter matrix prison refuse sense ordinary nose Index 2: mystery car occur shallow stable order number feature else best trigger curious

Use case

There are many use-cases for BIP85:

• Instead of worrying about backing up multiple mnemonics in a secure and resilient way, you can focus on storing only one.
• When you need a mnemonic for a less secure wallet (eg. browser extension), you can derive a new child mnemonic out of the master key. When a child key is compromised, other child keys and the master key are still safe.
• When you lose a child mnemonic, you can simply derive it again from your master seed. No backups of the child key are necessary.

Libraries

There was no bip85 library available in javascript, so I created one: https://github.com/AndreasGassmann/bip85

References

BIP85 Specs BIP39 tool from iancoleman PR

[AndreasGassmann]

This will be included in the next release

[AndreasGassmann]

It is included in 3.7.0