The easiest way to create secure offline bitcoin transactions

09 November 11

Warning: This mechanism is still in its early days so please use cautiously.

What's an offline Bitcoin transaction ?

An offline Bitcoin transaction is one created with a computer that is not attached to the internet (or any network). Assuming the installation process was secure the computer will not be prone to attack from hackers.

To create a Bitcoin payment the offline machine can create a Bitcoin transaction which can then be carried by a USB key or other means to a machine that is online and the transaction can be broadcast.

How do I create an offline transaction ?

There are several ways but the one I'm going to show is using a HTML page with some Javascript attached.

1. Download the offline transaction generator web page.

2. Retrieve the transactions for your account.

To populate the HTML form you've downloaded you'll need some information from the blockchain. The information needed is the transaction history for the Bitcoin key you want to send money from.

For example let's use 1BountYypWttTvAJcMJVvSRDfX3TJ182To to retrieve the information we need we type the following URL into our browser. http://blockexplorer.com/q/mytransactions/1BountYypWttTvAJcMJVvSRDfX3TJ182To

You need to cut and paste this page into a text document and transfer it to a USB key.

3. Create your transaction on your offline machine.

To do this you'll need the private key of the address you want to send from (in Base58) a destination address and the amount you want to send.

Cut and Paste the values into the HTML form (Should be fairly straight forward) and generate a transaction. Cut and the paste the transaction from the form field into a text file and place it on your USB key.

4. Submit the transaction to the Bitcoin network.

Go to http://bitsend.rowit.co.uk/ and cut and paste your raw transaction into the field and hit (press) submit.

Thanks To...

Thanks to BTCurious Offline TX generation and nibor Web page to cut and paste a transaction and to anyone else from the Bitcoin community that helped to make this happen.


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