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Crypto Swiss Knife

Secure Airgapped Transactions

Free Cold Wallets For Bitcoin, Ethereum, HEAT & FIMK

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Crypto Swiss Knife by heatledger.com is your trusted assistant for securely creating offline transactions for Bitcoin, Ethereum, HEAT, and FIMK. It ensures that your private keys remain airgapped and are never exposed to a network-connected machine.

Introduction

Performing smooth transactions while keeping your private keys offline is crucial for security. The Crypto Swiss Knife offers a browser-based user interface (UI) that you download as an HTML file and use on an airgapped computing device.

What Is an Airgapped Device?

An airgapped device is a computer that has no networking capabilities—it cannot connect to another device, and no device can connect to it. This isolation ensures that your private keys are not exposed to any network threats.

%% Define swimlanes
sequenceDiagram
    actor User as 😀 User
    participant AirgappedDevice as 💻
Airgapped
    participant NetworkedDevice as 💻
Networked
    participant HeatWallet as 📱
Heat Wallet
    participant Blockchain as 🌍
Bitcoin

    User ->> AirgappedDevice: Prepare Transaction
    NetworkedDevice ->> User: "Collect Required Data (Gas Price/UTXO)"
    AirgappedDevice ->> AirgappedDevice: Create Transaction & Generate QR Code
    HeatWallet ->> AirgappedDevice: Scan QR Code
    User ->> User: Verify Transaction
    HeatWallet ->> Blockchain: Broadcast Transaction

Airgapped transaction sequence

Step-by-Step Guide to Creating an Offline Transaction

1. Prepare the Airgapped Device

On your airgapped device:

  • Open the downloaded HTML file in a browser.
  • Navigate to the CREATE TRANSACTION tab (selected by default).

2. Select the Blockchain Network

Choose the network for which you are creating the transaction (Bitcoin, Ethereum, FIMK, HEAT), then click Continue.

3. Enter the Source

Enter the source, which can be either a recovery seed or a private key. The corresponding address will appear in the address field.

4. Gather Required Live Blockchain Data

Switch to your networked machine:

  • Open the Crypto Swiss Knife UI in a browser.
  • Go to the LOOKUP DATA tab.
  • Select the target blockchain and click Continue.
  • In the Source field, enter the address displayed on your airgapped device, then click Continue.

Depending on the blockchain, the UI will display information like gas price or nonce (for Ethereum), or required satoshi per byte and UTXO data (for Bitcoin).

5. Transfer Data to the Airgapped Device

Back on your airgapped device, enter the required information (nonce, gas price, satoshi per byte, and/or UTXO data), then click Continue.

Tip: To transfer UTXO data, you can use a USB stick. Copy the UTXO data from the networked device to a file and transfer it to the airgapped device.

6. Select Currency Type

Choose the currency type you wish to transfer. This applies to blockchains that support tokens. Possible choices include:

  • Native token types: Bitcoin, Ethereum, HEAT, or FIMK
  • Asset types: ERC20 token (Ethereum), HEAT Asset (HEAT), FIMK Asset (FIMK)

7. Enter Transaction Details

Input the recipient’s address and the amount to transfer, then click Continue.

8. Obtain the Raw Transaction Bytes

You will now see the raw transaction bytes. To broadcast this transaction to the network, you have two options:

  • Option 1: Scan the transaction QR Code with the Heat Wallet app on your mobile device.
  • Option 2: Copy the transaction hex data back to the networked device and use the Crypto Swiss Knife UI.

Broadcasting the Transaction

Option 1: Broadcast Through Heat Wallet (Recommended)

Using a device with a camera, you can use the Heat Wallet app to broadcast and track your transaction. This is the recommended method as it allows you to verify transaction details before broadcasting.

Steps:

  1. Open the Heat Wallet app on your mobile device.
  2. Open the menu by tapping the button in the top-left corner.
  3. Tap GO TO SETTINGS at the bottom of the menu.
  4. Choose Broadcast Transaction.
  5. Select the blockchain network on the next screen.
  6. Tap the SCAN button to open the camera finder.
  7. Scan the QR code displayed on your airgapped device.

Heat Wallet will parse the raw transaction bytes from the QR code, verify the signatures, and display all transaction details, including:

  • Transaction ID
  • Sender address
  • Recipient address
  • Value
  • Fee amount and details
  • UTXO information (inputs and outputs for Bitcoin)

Review the transaction details to ensure they match your expectations. Once verified, proceed to broadcast the transaction.

Before broadcasting, Heat Wallet will create a new READ ONLY WALLET for you. This wallet is based on the address alone and cannot be used to create transactions, but it allows you to track the balance and transaction history.

Option 2: Broadcast Through Crypto Swiss Knife (Not Recommended)

Alternatively, you can transfer the signed transaction bytes back to the networked device via a USB stick and use the Crypto Swiss Knife UI to broadcast.

Steps:

  1. Go to the BROADCAST TRANSACTION tab in the Crypto Swiss Knife UI on the networked device.
  2. Select the target blockchain network.
  3. Enter the amount you are sending and the hexadecimal raw transaction bytes.
  4. Click Broadcast to send the transaction to the network.

Warning: This method is not recommended because it does not allow verification of the signed transaction’s contents. Using the Heat Wallet with a QR code is preferred as it enables you to verify the recipient’s address and other transaction details.

Future Plans

  • Support for Other Derivation Paths: Ability to select different derivation paths from the recovery seed (currently selects the first external address).
  • Support for Other Bitcoin Address Types: Inclusion of additional Bitcoin address types (currently defaults to P2PKH addresses).
  • Support for Other Blockchain Networks: Expansion to include more blockchain networks.
  • Multi-part QR Code Data Transfer: Implementation of a multi-part QR code mechanism to transfer larger payloads like UTXO data.

Conclusion

The Crypto Swiss Knife by heatledger.com provides a secure and efficient way to create and broadcast transactions while keeping your private keys offline. By following the steps outlined above, you can confidently manage transactions across multiple blockchain networks with enhanced security.

Note: This document has been revised for improved readability and organization. It includes suggestions for images and screen recordings to enhance understanding. The front matter has been updated for better metadata and SEO optimization.