Sweep to Cold Storage
Complete guide to moving your Bitcoin from mobile wallets to hardware security
Moving Bitcoin to Hardware Cold Storage
This guide provides step-by-step instructions for securing your Bitcoin in cold storage using hardware wallets. Follow these detailed steps to ensure your Bitcoin is safely transferred from mobile wallets to long-term secure storage.
Table of Contents
- Understanding Cold Storage
- Preparing for the Transfer
- Setting Up Your Hardware Wallet
- Transferring Bitcoin from Mobile Wallets
- Verifying Your Transfer
- Best Practices for Cold Storage
- Recovery and Backup Procedures
- Advanced Cold Storage Options
Understanding Cold Storage
Cold storage refers to keeping your Bitcoin private keys offline on a dedicated hardware device, dramatically reducing potential attack vectors compared to mobile or online wallets.
Benefits of Hardware Wallets
- Enhanced Security: Private keys never leave the device
- Protection from Malware: Immune to computer viruses and keyloggers
- Physical Verification: Transactions require physical confirmation
- Disaster Recovery: Built-in backup and recovery options
- Long-term Storage: Designed for secure, long-term Bitcoin storage
When to Use Cold Storage
Cold storage is recommended when:
- Your Bitcoin holdings exceed $1,000 in value
- You plan to hold Bitcoin for more than 6 months
- You want maximum protection against remote attacks
- You’re creating a long-term savings plan or inheritance
Preparing for the Transfer
Before beginning the transfer process, prepare the following:
- Hardware wallet device (Bitkey, ColdCard, or Trezor)
- Pen and paper for recording recovery phrases
- Secure location free from cameras or onlookers
- Mobile wallet with Bitcoin to transfer
- Small amount for testing (always send a test transaction first)
- Time without distractions (30-60 minutes for setup)
- Stable internet connection (for the mobile wallet side)
Setting Up Your Hardware Wallet
Each hardware wallet has a specific setup process. Select your device below:
About Bitkey
Bitkey uses a "two-of-three" multi-signature security model with a mobile app component, hardware component, and recovery key component.
Setting Up Your Bitkey
Initial Hardware Setup
Unbox your Bitkey hardware device
Power on by pressing the circular button
Follow on-screen instructions to set up your device PIN
Verify the device displays an untampered seal message
Install the Bitkey Mobile App
Download the Bitkey app from the App Store or Google Play
Open the app and select "Set up a new wallet"
Follow the pairing instructions to connect to your hardware device
Create a secure PIN for the app
Create Your Recovery Key
When prompted, the app will guide you through creating a recovery key
Write down all 12 or 24 seed words IN ORDER on provided recovery cards
Verify each word carefully - these words ARE your Bitcoin
Store recovery cards in a secure, private location
Verify Your Setup
Complete the recovery phrase verification test on both devices
Ensure both the hardware and mobile components show the same wallet balance
Test the approval process for a small transaction
Creating a Receive Address with Bitkey
Connect Your Wallet
Open the Bitkey mobile app on your smartphone
Ensure it's properly paired with your hardware device
Verify both devices are powered on and responsive
Generate Address
Tap "Receive" in the mobile app
The app will generate a new Bitcoin address
Your hardware device will display a verification request
Verify Address
Important: Confirm the address matches on both mobile and hardware devices
This verification step protects against address replacement attacks
Never use an address you haven't verified on the hardware device
Label the Address (Optional)
Add a description like "Flash Transfer - March 2025"
This helps track the source of funds later
Labels are stored locally and not on the blockchain
About ColdCard
ColdCard is a Bitcoin-only hardware wallet that can operate completely air-gapped and offers advanced security features.
Setting Up Your ColdCard
Initial Hardware Setup
Unbox your ColdCard
Insert a microSD card (optional but recommended)
Connect the device using the included USB cable
Create a new wallet when prompted
Set up a strong PIN with both a prefix and suffix
Backup Your Seed Words
Carefully write down all 24 seed words in order
Double-check each word against the ColdCard screen
Consider stamping seed words on metal for fire/water resistance
Secure your backup in a safe location
Advanced Security Setup
Set up a BrickMe PIN (emergency delete function)
Configure Duress PIN if desired (shows limited funds)
Set up a passphrase for additional security (optional)
Test your PINs to ensure they work correctly
Install Companion Software
For desktop interaction, install Sparrow Wallet
Connect your ColdCard via USB or use the microSD card for air-gapped operation
Export the wallet public key to Sparrow using the microSD card
Verify the wallet appears correctly in Sparrow
Creating a Receive Address with ColdCard
Connect Your Wallet
Option 1 (USB): Connect ColdCard via USB cable to your computer
Option 2 (Air-gapped): Use microSD card for complete isolation
Open Sparrow Wallet on your computer
Generate Address
In Sparrow Wallet, select the "Receive" tab
Choose the address type (Native SegWit recommended)
Sparrow will display a new Bitcoin address and QR code
Verify Address
Crucial security step: Verify the address on ColdCard's screen
On ColdCard, navigate to Address Explorer
Compare the address shown in Sparrow with the one on ColdCard
Only proceed if addresses match exactly
Label the Address (Optional)
In Sparrow, add a label such as "Flash Transfer - March 2025"
This helps you track which deposits came from where
Labels are stored in Sparrow, not on the blockchain
About Trezor
Trezor offers an intuitive user experience with a simple interface while maintaining strong security.
Setting Up Your Trezor
Initial Hardware Setup
Unbox your Trezor device
Connect it to your computer via USB cable
Visit trezor.io/start
Follow the on-screen instructions
Create a new wallet when prompted
Create Device PIN
Create a strong PIN following the on-screen instructions
The PIN entry uses a randomized keypad for protection
Remember this PIN - it protects physical access to your device
Backup Recovery Seed
Write down all 12 or 24 seed words in exact order
Verify the recovery seed when prompted by the setup wizard
Store in a secure, private location away from potential threats
Consider creating a metal backup for fire/water resistance
Setup Trezor Suite
Install Trezor Suite on your computer
Connect your device and unlock it with your PIN
Create a Bitcoin wallet in Trezor Suite
Optionally add a passphrase for additional security
Creating a Receive Address with Trezor
Connect Your Wallet
Connect Trezor to your computer via USB cable
Open Trezor Suite on your computer
Unlock your device with your PIN
Enter passphrase if you've set one up
Generate Address
In Trezor Suite, click on the "Receive" tab
Select the account you want to receive to (if multiple)
Choose address type (Native SegWit recommended for lower fees)
Trezor Suite will generate a new Bitcoin address
Verify Address
Trezor will prompt you to confirm the address on the device
Compare the address on your screen with the one on Trezor
Only approve if they match completely
This step protects against malware that might try to display fake addresses
Label the Address (Optional)
Add a descriptive label like "Flash Transfer - March 2025"
Trezor Suite will save this label with the address
Makes it easier to identify funds and their source later
Transferring Bitcoin from Mobile Wallets
Now you’re ready to send Bitcoin from your mobile wallet to your hardware wallet:
From Flash Wallet
Open Flash App
Go to the "Wallet" tab
Ensure you have sufficient balance
Check that your Lightning channels have enough outbound capacity
Initiate Transfer
Tap "Send" or "Withdraw"
Select "On-chain withdrawal"
Note that on-chain withdrawals have higher fees than Lightning
Enter Details
Paste your hardware wallet's receive address
Double-check the address is correct (first and last few characters)
Start with a small test amount (e.g., 0.0001 BTC or 10,000 sats)
Enter an amount that's high enough to cover network fees
Review and Confirm
Check the withdrawal fee (higher fees confirm faster)
Prioritize security over saving on fees for cold storage transfers
Verify all details are correct one final time
Tap "Confirm" to initiate the transfer
Initial Test Verification
Wait for the test transaction to confirm (10-60 minutes)
View the transaction status in the Flash app
Verify receipt on your hardware wallet
Once confirmed, proceed with transferring larger amounts
From Other Mobile Wallets
Open Your Mobile Wallet
Access the wallet containing your Bitcoin
Navigate to Send/Transfer function
Make sure your wallet is updated to the latest version
Enter Hardware Wallet Address
Paste your verified hardware wallet address
Double-check the entire address if possible
For large transfers, verify the address through multiple channels
Never manually type addresses - always copy and paste
Set Transaction Fee
Choose an appropriate fee based on urgency
For cold storage, medium priority is usually sufficient
Check mempool.space for current fee recommendations
Consider the tradeoff between confirmation time and cost
Send Test Transaction
Start with a minimal amount (0.0001 BTC or equivalent)
Review all details before confirming
Confirm the transaction in your wallet
Record the transaction ID/hash for reference
Complete the Transfer
After confirming receipt of test transaction
Send remaining amount in one or multiple transactions
Consider privacy implications of transaction patterns
Keep transaction IDs for future reference
Security Reminder
Always verify the receiving address on your hardware wallet's secure screen before sending any funds. A compromised computer could display a different address than the one you intended to use.
Verifying Your Transfer
After sending, verify the transfer was successful:
Check Transaction Status
- Use a block explorer like mempool.space
- Enter your transaction ID or wallet address
- Monitor confirmations (6+ is considered extremely secure)
Verify on Hardware Wallet
- Bitkey: Check balance in both mobile app and hardware device
- ColdCard: Check balance in Sparrow Wallet or via microSD export
- Trezor: Check balance in Trezor Suite
Document the Transfer
- Record the transaction ID
- Note the date, amount, and sending address
- Store this information securely for future reference
Best Practices for Cold Storage
Maximize your security with these best practices:
Multiple Hardware Wallets
- Consider using different brands for diversification
- Separate wallets for different purposes (spending vs. long-term)
Regular Verification
- Check device functionality every 6-12 months
- Update firmware when security updates are released
- Perform test recoveries annually
Secure Storage Environment
- Keep hardware wallets in cool, dry locations
- Protect from electromagnetic interference
- Consider a fireproof, waterproof container
Physical Security
- Don’t discuss hardware wallet ownership publicly
- Consider a home safe or bank safety deposit box
- Have a “decoy” wallet with small funds if concerned about physical threats
Avoid Common Mistakes
- Never enter seed phrases on a computer or phone
- Don’t store seed phrases in cloud services or digital formats
- Don’t share photos of seed phrases or hardware wallets
- Beware of phishing attempts targeting hardware wallet users
Recovery and Backup Procedures
Prepare for emergencies with proper backup procedures:
Seed Phrase Protection
- Store seed phrases separately from hardware devices
- Consider metal backup solutions (Cryptosteel, BlockPlate, etc.)
- Split backups across multiple secure locations
Test Recovery Procedure
- Practice recovery without actual funds
- Understand the process before an emergency
- Document steps for heirs or trusted individuals
Inheritance Planning
- Create clear instructions for heirs
- Consider multi-signature setups for inheritance
- Establish legal frameworks appropriate to your jurisdiction
Advanced Cold Storage Options
For users seeking maximum security:
Multi-Signature Setups
- Require multiple devices to approve transactions
- Distribute risk across different security models
- Popular options: Sparrow Wallet multisig, Caravan
Air-Gapped Operations
- Keep signing device completely offline
- Transfer transaction data via microSD or QR codes
- ColdCard and some Trezor models support this workflow
Geographic Distribution
- Store backup components in different physical locations
- Consider jurisdictional diversification for large holdings
- Balance security with practical accessibility
Need Help?
If you encounter any issues during the transfer process, reach out to Flash support through the app or visit our community forums for assistance.