Bitcoin Core (CLI) with a hardware key via HWI (Ledger or Trezor).
That would imho be the most secure "wallet".
But storing Bitcoin in a cold wallet is even better.
Creating a Bitcoin Cold Wallet with Bitcoin Core, HWI, and Ledger
A Ledger keeps your Bitcoin private keys off your computer, while Bitcoin Core lets you verify transactions through your own node. HWI connects Bitcoin Core to the Ledger.
What You Need
- A genuine Ledger hardware wallet
- Bitcoin Core
- Hardware Wallet Interface — HWI
- Ledger Wallet to install the Bitcoin app
Basic Setup
- Set up the Ledger
Initialize the Ledger as a new device and write down its recovery phrase by hand.
Never photograph, type, upload, or store the recovery phrase on a computer.
- Install the Bitcoin App
Use Ledger Wallet to update the device and install the official Bitcoin app.
- Install and Sync Bitcoin Core
Install Bitcoin Core from its official website and allow it to fully synchronize with the Bitcoin network.
This may require substantial disk space and several hours or days.
- Install HWI
Download and install Hardware Wallet Interface from the official Bitcoin Core HWI project.
- Connect the Ledger
Connect and unlock the Ledger, then open the Bitcoin app on the device.
Use HWI to detect the Ledger and create a hardware-backed wallet in Bitcoin Core.
- Receive Bitcoin
Generate a receiving address through the wallet.
Always confirm that the address displayed by Bitcoin Core matches the address shown on the Ledger screen before sending funds.
- Send a Small Test Amount
Send a small amount of Bitcoin to the new address and wait for it to confirm before transferring a larger balance.
- Sending Bitcoin Later
Bitcoin Core prepares the transaction, but the Ledger must physically approve and sign it.
The private keys and recovery phrase should never leave the Ledger.
Important Security Rules
- Only download software from official sources.
- Never enter your Ledger recovery phrase into HWI, Bitcoin Core, Ledger Wallet, a website, or a computer.
- Store the recovery phrase securely in at least one protected offline location.
- Verify receiving addresses on the Ledger screen.
- Test the setup with a small amount first.
- Anyone who obtains the recovery phrase can take the Bitcoin.
Note: This is more accurately described as a hardware-wallet setup than a completely air-gapped cold wallet. The private keys remain isolated inside the Ledger, but the device is temporarily connected to the computer when signing transactions.