Understanding BIP 85 and Deterministic Entropy

Hey folks, So, about BIP 85. I get that I can create deterministic entropy for making mnemonic phrases for different wallets, passwords, WIF keys, and all that jazz. I’m using a coldcard MK4 for this right now. Here’s my question: what if I lose access to the coldcard? As long as I have the mnemonic phrase, or the mnemonic phrase + BIP 39 passphrase if I want to use it, can I use another app to generate this deterministic entropy, or is it just a coldcard thing? Also, I checked out the bip85.com site, and under long-term hodl best practices, it says, "We still recommend people keep their deep cold hodl funds separate from their spending funds. It's best to have one or more master seeds for your spending wallet and one or more master seeds for your long-term hodl. Use a spending master seed to generate more spending seeds. It's important to segregate funds." Can anyone break this down for me? Is it okay to have one long-term hodl wallet and maybe two spending wallets? Thanks for your help!

As long as it is BIP39 seed phrase and passphrase, there are other wallets that you can import both to generate your keys and addresses and also use for spending the coins. There are many BIP39 wallets, you have nothing to worry yourself about. Do what is best for yourself. You can have more than one hardware wallet or cold wallet. If you have more than one, the better you are.

It's not specific to ColdCard. That is based from BIP85 which is the set "Standard" for it. Means that other wallets that want to implement a similar feature would have to use its proposed method or they'll have an incompatible "niche" wallet. For example, you can use IanColeman's BIP39 tool to compute the child key mnemonic by ticking "Show BIP85" option. (same as the ones you selected in "Derive Seed B85" in ColdCard). But do not actually use it just for testing specially online; if you really need to test, do it on a permanent Air-Gap machine. This is simply for your long term HODL's safety since you wouldn't want to link it to your master BIP85 seed which if hacked, all of the linked wallets will be compromised. So create a separate new master seed mnemonic for your HODL wallet, not created by your regular wallets' master seed.

Your main question seems to be whether it is possible to regenerate the values derived by BIP-85 (child seed, WIF, passwords) without a coldcard... the answer is yes. BIP-85 is available on other hardware wallets such as Passport2, bitbox02, Jade, and more. You can check the full list of supported devices here: https://thebitcoinhole.com/hardware-wallets. However, coldcard is the only one that supports BIP-85 passwords (I've heard that Passport2 and Krux have BIP-85 passwords, it would be good if someone showed a screenshot of the feature to update my topic). But even if you don't have any of these hardware, you can still use BIP-85 with these tools: Ian Coleman BIP39 and bitcoiner.guide/seed (this one includes BIP-85 Passwords support) To reinforce nc50lc’s response, if you derive BIP-85 values from your master seed, do it in a 100% offline and air-gapped environment that will never be connected to the internet again. There is no need to expose your original seed elsewhere. You can generate a child seed to test in other environments, because naturally, it is not possible to reverse engineer the child key's xpriv to get to the original value, which is your master seed. This is the security of BIP-85, knowing how to use it. Obviously, generate your child seeds on coldcard first, we don't want to compromise the parent seed. If you plan to test the tools i mentioned (ian coleman or bitcoiner.guide/seed), they work online, but the .html page also works offline, which is the correct way to use them, unless you're just playing around and testing without exposing any master seed from your cold storage or any child seed with real funds. In any case, if you decide to use them offline, download the .html file or clone it directly from github and verify the signatures of the downloaded files to ensure you have obtained the original files! I won’t go into too much detail here, but if you want to learn more about BIP-85, i created a dedicated thread with the best references i could find on the web.

Thank You both for responding. Yes, if i ever need to use bip85 beacuase say my coldcard is missing and i may need to retrieve some deterministic entropy, then yes I will do it in an offline fashion, maybe using something like tails. I have been learning more about BIP85, And, yes, I am aware , that if a child mnemonic phrase is compromised that it cannot be used to derrive the master seed or even other child seeds.Yes, all entropy would be generated on coldcard. Any use of the protocol outside of the coldcard would only be in an emergency, and under the most carefull conditions, offline etc... Besides the links you posted, i also found a set of python libraries called bip utils that will handle all of the different types of entropy, 12 word, 24 word, wif, password, etc... I will take a look at the thread you posted, and I look forward to learning all the details about this great protocol, Thank You guys again for contributing.