Preparation

The Withdrawal Protocol is used to transfer bitcoins out of high-security cold storage.

Before beginning, consider whether you want to route your funds through one or more intermediary non-cold-storage addresses for privacy purposes. (Review the Privacy Considerations subsection for details.) If you do, you may want to withdraw the funds to an intermediary address first before sending them on to their final destination.

In this first section, we’ll gather physical hardcopies of all information needed to do the withdrawal. This is done with the help of a regular networked computer to find some of this information online and translate it into printed QR codes.

On any Internet-connected computer:

1. If this is not your first time working with Glacier:
   1. Use a networked computer to access the latest full release of Glacier ( not just the protocol document) at https://github.com/bitcoinfacts/GlacierProtocol/releases/latest.
   2. Check the Release Notes to see if there are any new versions of Glacier recommended.
   3. Whether or not you decide to upgrade, review the errata for the version of Glacier you are using at https://github.com/bitcoinfacts/GlacierProtocol/releases.
2. Open your electronic copy of the Cold Storage Information Page (see Section II of the Deposit Protocol for details).
3. Identify the blockchain transactions associated with the funds you’d like to withdraw:
   1. If you have you have your own Bitcoin node, such as Umbrel:
      1. SSH to it:

          $ ssh umbrel@umbrel.local
         

      2. Then run:

         $ ~/umbrel/bin/bitcoin-cli scantxoutset start '["addr(cold sto
          rage address)"]'

      3. It will take 1-2 minutes to complete. It will list all unspent transactions for the given address.
   2. If you don’t have your own Bitcoin node:
      1. Go to Blockstream, paste your cold storage address into the search bar, and press Enter.
      2. You’ll be taken to a page that says “Address” at the top, with your cold storage address listed underneath.
      3. Below that, the page will show a list of transaction IDs (on the left) and their corresponding amounts (on the right). Each transaction ID corresponds to a deposit you made, the remainder of a deposit you made after doing a partial withdrawal, or a deposit someone else made to your cold storage address.
      4. For each transaction, click on the “Details” button to determine whether the transaction has some unspent amount (the “Spending Tx” field will be shown as “Unspent”).
   3. Identify a set of transaction IDs whose unspent amounts are cumulatively greater than or equal to the amount you would like to withdraw. If a transaction ID is listed more than once (i.e. the same transaction has more than one unspent output going to your cold storage address), you just need to include the transaction ID once. GlacierScript will include all UTXOs in every supplied transaction ID.
   4. Copy-paste these transaction IDs to a temporary scratchpad for reference. These will be referred to as unspent transaction IDs.
4. Get raw data for blockchain transactions:
   1. For each unspent transaction ID from your temporary scratchpad:
      1. If you have your own Bitcoin node, run:

         $ ~/umbrel/bin/bitcoin-cli getrawtransaction transaction-id-here

      2. Otherwise, go to the following URL, substituting the unspent transaction ID in the specified place: https://blockchain.info/rawtx/transaction-id-here?format=hex

         Example page contents:

         01000000016847105309a8604c7e4f5773d0a16c45248acce057dab62e
         db0fedc2810d49a4010000006b48304502210093e6b4154d42c1bba27c
         548a80488673967be32c8de2f11e01a1402a5500e13302203e20874e5d
         0af516c902d3b600ee94571a7ce68a14a384dc05d4346e1009fe000121
         039fd6f25c87f183260c1d4a3a3ae33a2c06414db4c40d0c2ab76a7192
         1fef0939ffffffff01e0930400000000001976a914e770a7c13f977478
         3e80607f40be4547780315b688ac00000000

   2. This entire page be referred to as a raw unspent transaction.
   3. Copy-paste the raw unspent transaction next to the unspent transaction ID in your temporary scratchpad.
5. Create QR codes:
   1. Find an online QR code generator, such as http://goqr.me.
   2. For each unspent transaction ID in your temporary scratchpad:

      1. Copy-paste the raw unspent transaction into the QR code generator.

         NOTE: Some raw unspent transactions are too long to be converted into a single QR code – or the QR code may be such high resolution that some QR code readers may struggle to read it.

         In these cases, you will need to split the data into multiple QR codes, and manually splice them back together on the quarantined computer after decoding each QR codes.

         Make sure there is no extra whitespace (i.e. a space, or pressing “Enter”) at the end of any copy-pastes! This can change the QR code.

      2. Print out the resulting QR code. (If printing from goqr.me, just print the first page.)
      3. Write “raw unspent transaction” somewhere on the printout.
   3. Repeat step (b) above for other needed information:
      1. Cold storage address (from the Cold Storage Information Page)
      2. Redemption script (from the Cold Storage Information Page)
      3. Destination address to which you will be withdrawing the funds:
         1. Carefully transcribe the destination address by hand on the printed page with its QR code. (This will facilitate verification in the quarantined environment.)
         2. Double-check that the transcribed address is correct.
         3. If you are sending funds directly to another party with whom you do not have high trust, be mindful of the risk of transaction malleability fraud.
6. Gather other information:
   1. Make sure you have the necessary number of Cold Storage Information Packets on hand (you’ll need the private keys).
      1. For the recommended 2-of-n multisignature withdrawal policy, you’ll need any 2 Cold Storage Information Packets.
      2. If you are performing an initial test withdrawal, you’ll need all Cold Storage Information packets.

   2. Get transaction fee market data:

      The operators of the Bitcoin network require a (very small) fee for processing transactions. There is not a fixed fee schedule; if the fee is too low, the withdrawal will never get processed, and if the fee is too high, you unnecessarily waste money. This data will be used to calculate a reasonable fee for expedient transaction processing.

      1. Note that different services return fee estimates in different units. We are interested in the rate of satoshis / byte (or vbyte) rather than satoshis / kilobyte (or kB) or BTC / kB. 1 satoshi = 10^-8 BTC and a typical transaction is under 1000 bytes. As of late 2019, between 1 and 100 satoshis / byte is typical. If the number is radically higher than 100 or less than 1, stop; something may be wrong. Seek assistance.

      2. If you are running a Bitcoin Core full node, you can run:

          $ bitcoin-cli estimatesmartfee 6
         

         This returns a fee rate in BTC/kB; multiply the result by 100,000 to get satoshis / byte.

      3. Otherwise, use a service listed at https://b10c.me/A-list-of-public-feerate-estimator-APIs/

      4. Write the fee estimate corresponding to your desired confirmation time on a piece of paper labeled “Fee rate.” Round up to the nearest whole number in units of satoshis / byte.