Can I use the same hardware wallets across multiple accounts?

Yes, but you must change the BIP32 derivation path.

If you need to, you can always use your two existing keys to create multiple vaults and loans in your Unchained account. Separately, you can also use your same hardware wallets for multiple accounts. For example you may have personal, business, and IRA accounts but only want to use two hardware wallets in total.

Note: If you want to create multiple vaults on the same account, you don't need to follow these steps. To do that, simply create more vaults!

How to upload multiple keys from the same hardware wallet

  1. Sign in to your Unchained account.
  2. Upload a new account key by clicking New under Keys.
  3. In the Export extended public key section, click the 3 dots in the top right corner. Then choose show advanced. This allows you to specify your BIP32 derivation path. 
  4. Enter a BIP32 path that has not been used yet. You can change the BIP32 path by changing the third depth number. (You can choose m/45'/0'/1' if it's the second time you're uploading a key from the same hardware wallet (m/45'/0'/0' being the first used.)
    • Note for Coldcard users: When exporting your xpub, the Coldcard may ask you to enter an "account number."  Always enter 0 for the account number, even when changing the BIP32 derivation path.
  5. If you see an apostrophe after the depth number, do not remove it if you're using a Ledger or Trezor. Coldcards do not use apostrophes after the last digit.
  6. Now that you've changed the derivation path, proceed with the key upload as normal. Because of the path change, your hardware wallet will share a different xpub.

Caution: These steps are intended to be used across separate accounts. Do not use the same hardware wallet twice on the same account. This introduces a single point of failure and degrades security of the multisig setup.