cold storage via brainwallet.org

[lyth0s]

Hello I have an offline pc that i used to generate a private/public BTC address. I then sent myself bitcoins to the offline address and I can confirm it is in there. Now my question is when I want to send a transaction from my offline pc (with brainwallet.org client javascript) how do I actually create the raw transaction data to send the transaction? My plan is to create the raw transaction on the offline pc, put it on a usb text file, then submit it to the block chain via blockchain.org.

My problem is that on the create transaction page from the brainwallet javascript I don't know what i have to do to be able to spend my unspent outputs or something along those lines...basically the client wants to access blockchain.info so it knows what to spend.

Any help is greatly appreciated.

[cp1]

You can use the public address on an online computer with blockchain.info/listunspent to get the info you need.

But please I hope you didn't generate your keys using a brainwallet passphrase instead of a randomly generated one.  If so, your coins won't stay safe for long.

[lyth0s]

even if it is over 60 alphanumeric + symbols long with none of it being from a dictionary?

[lyth0s]

You can use the public address on an online computer with blockchain.info/listunspent to get the info you need.

But please I hope you didn't generate your keys using a brainwallet passphrase instead of a randomly generated one.  If so, your coins won't stay safe for long.

blockchain.info/listunspent doesnt work. If i choose a random address such as this one...is this what im looking for? and how does this fit into the brainwallet json?
http://blockchain.info/unspent?active=19kf1pxJaZqFmFeupSL9WViS6ExsVSKLc3&format=html

[cp1]

even if it is over 60 alphanumeric + symbols long with none of it being from a dictionary?

A real private key is only 51 characters, just use that.

[lyth0s]

even if it is over 60 alphanumeric + symbols long with none of it being from a dictionary?

A real private key is only 51 characters, just use that.

easier for me to remember if i get to make it up

What info do i need though from blockchain?

[cp1]

You need the tx of the unspent input, its n, and the amount.  Be careful or you could end up spending all your bitcoins in fees.

[lyth0s]

That is scary, how do i avoid that?

Edit: Could I use an online brainwallet with the public address to create the json, then on my offline pc input the private address and create the raw transaction?

[Abdussamad]

even if it is over 60 alphanumeric + symbols long with none of it being from a dictionary?

A real private key is only 51 characters, just use that.

easier for me to remember if i get to make it up

That right there is the problem. If you made it up then it doesn't matter how long it is it is not random enough to be a secure passphrase.

My suggestion to you is that you install electrum on your offline PC. It can function both as a brain wallet and a full fledged offline wallet.

[lyth0s]

if electrum private keys can be restored using 12 dictionary words for the seed, isn't that less secure?

[Abdussamad]

if electrum private keys can be restored using 12 dictionary words for the seed, isn't that less secure?

No, but I understand where this is coming from. This was one of the first questions I asked about Electrum too:

https://bitcointalk.org/index.php?topic=153990.msg1883397#msg1883397

The seed is a 128bit random number generated by a computer. Computers are better at generating random numbers than human beings. The seed in words is merely a human friendly representation of the numerical seed. Changing the way it is presented does not change the fact that it has 128bits of entropy.

Edit: Also if you want to know why human generated passphrases are a bad idea see this post from a bitcoin-qt developer:

https://bitcointalk.org/index.php?topic=311000.msg3345309#msg3345309

[lyth0s]

if electrum private keys can be restored using 12 dictionary words for the seed, isn't that less secure?

No, but I understand where this is coming from. This was one of the first questions I asked about Electrum too:

https://bitcointalk.org/index.php?topic=153990.msg1883397#msg1883397

The seed is a 128bit random number generated by a computer. Computers are better at generating random numbers than human beings. The seed in words is merely a human friendly representation of the numerical seed. Changing the way it is presented does not change the fact that it has 128bits of entropy.

Edit: Also if you want to know why human generated passphrases are a bad idea see this post from a bitcoin-qt developer:

https://bitcointalk.org/index.php?topic=311000.msg3345309#msg3345309

Thank you for that reference. Time to move away from my brain wallet