Introducing the Bitcoin Time Capsule. You don't have to trust a lawyer or other third-party to ensure your family has access to your bitcoin. Create a timelocked wallet on BTCapsule, and when the time comes, your bitcoin will be available to whomever you choose.
BTCapsule creates a P2SH address that is timelocked to 500,000,001 (one second above the earliest timestamp recognized by the Bitcoin network) at the script level. The sender wallet contains a raw transaction that is timelocked to 500,000,001 at the transaction level and allows you, the original holder, to redeem your Bitcoin at any time. The receiver wallet contains a raw transaction that is locked at whatever date you choose, which is then converted to a unix timestamp.
How Does It Work?
PLEASE FOLLOW THESE DIRECTIONS CAREFULLY
BTCapsule is a Python program that can run on an Android device.The directions to build BTCapsule are very easy. Once BTCapsule is ready, the directions are quick and simple:
1. Click "Generate" to create a P2SH address and a new Sender's Wallet
2. Add funds by copying the P2SH address into your mobile wallet or scanning the QR code
3. Enter a future date
4. Enter the txid/hash and vout (0 or 1) of the transaction you created in step 2. *
* To find the txid/hash,visit a block explorer and paste the P2SH address into the search box. The easiest way to copy the txid is tovisit a QR Creator website, paste the txid, and scan the QR code with your Android device.
5. Enter the amount of bitcoin you sent to the P2SH address, minus tx fees. *
* If you enter the full amount sent to the P2SH address, the miner fee will be 0 BTC. This can cause the transaction to get stuck as miners process transactions that offer them more BTC.
Once you hit Enter, this will create two folders with several files. These files are very important and must be kept safe.
1. The main folder is called sender_files, and it contains all the files created by BTCapsule. The sender_wallet is your private keys and a redeem script to redeem your bitcoin at any time.
2. The receiver_files folder is the folder you will give to your loved one, so copy it to another flash drive. It includes everything they need to redeem your bitcoin on the chosen date.
It is recommended that you disable internet connection before using BTCapsule. You may also want to print your paper wallet as a backup, but make sure to keep it in a secure location.
That is it! You can now give your BTCapsule to your children or a loved one. If they try to redeem the bitcoin before the date you selected, they will be prompted to wait.
How To Use The Redeem Script?
In your generated paper wallet, there is a section called Redeem Script. It will be the longest string of numbers and letters. This is called a "signed raw transaction".
When you are ready to redeem, copy the string and paste it in a block explorer. There is also a QR code you can scan with another device to quickly copy the string. I recommendBlockstream.info, but you can just Google "broadcast bitcoin transaction" for more options.
This will send the bitcoin to the address in your generated paper wallet. Once the transaction is confirmed on the Bitcoin network, you can open BTCapsule and use the Sweep Wallet feature.
The directions are very simple:
1. Enter any address you wish to send the Bitcoin to
2. Enter the amount of Bitcoin you have stored in the wallet, minus miner fees. If you're unsure how much is available, visita block explorer and copy your "Public Address" into the search box. The amount will be listed under the "Confirmed Unspent" or "Final Balance" section.
When you redeem, you will need to input a smaller amount to pay for miner fees. If the block explorer complains that there is not enough bitcoin, simply subtract more satoshis and try again.
Miner fees
You must pay miner fees to ensure your transaction is successful. You do this by subtracting miner fees from the amount you sent to the P2SH address and inputting the difference in the BTC field.
Although transaction fees may cost more fiat in the future, as the price of Bitcoin increases, choosing the current standard miner fee will be more than enough to ensure success.
However, this also means that you will be paying a much higher transaction fee the longer you timelock your Bitcoin. Suppose you choose a miner fee of 0.00005 BTC. Currently, that is about $0.85 in 2022. In 2045, that could be well over $5. Not a huge deal, but something to be mindful of.
HELP! I'm getting an error message!
After you create your timelocked wallets, I advise you to go ahead and broadcast the redeem script in the receiver_wallet.txt file. You should see a message that says "non-final". This means the transaction is timelocked, and the script cannot be redeemed until the date you chose.
(*You may see Transaction Not Found. If you see this, simply refresh the page. If that doesn't work, press the back button and try again. This happens sometimes, but its not a big deal.)
However, if you made a mistake (wrong vout number) and see a different message, don't worry! Your coins are not lost forever.
1. Rename the sender_wallet.txt file to anything (ex. sender_wallet_old.txt). DO NOT DELETE THIS FILE!
2. Delete or rename the receiver_wallet.txt file
3. Open BTCapsule and do NOT hit "Generate"
4. Fill out the form with the information stored on your sender_wallet
5. Triple check that you have the right txid and vout number
That's it! This will create two new wallets. The senders wallet will be exactly like the old wallet, except the redeem script will be a little different. Try again, and if everything works, delete the old sender_wallet
Why Do I Need It?
According to a 2020 report from Chainalysis, an estimated 3.7 million Bitcoin are gone forever. Some people forget or misplace their private keys, and unfortunatly, many people have passed away without providing their family access to their Bitcoin.
With BTCapsule, you have nothing to worry about. You have complete control over your bitcoin, and if you're (hopefully) still alive when the date you choose approaches, simply redeem your own bitcoin and create a new timelocked transaction.
BTCapsule does not require the internet to create a transaction. You must use the internet to install the apps from the App Store and install the dependencies into Pydroid.
Once BTCapsule is built, it is highly recommended that you disconnect the internet and never give internet access to your Android device again.
