How to create OFFLINE Transaction?

[BTCIndia]

Private key is converted into public key from one way cryptography thereafter it is used to sign transaction etc etc. Is it possible to create a offline transction?

I mean do all necessary things offline then it would result in some "lengthy random string" which can only be understand and processed by network. Once that lengthy random string is made we can convert into some hash of 32 bytes. Then write it on paper and then decrypt '32 bit hash'  with computer connected to internet to yield "lengthy random string" which can be broadcast to network?

I don't know much about cryptography. But, I think. It is possible. How can I do it to ensure security of my private key?

[pooya87]

yes in fact there is a way. i don't know about other desktop wallets but in Electrum you can do this easily
take a look at "How to make offline transactions using your Master Public Key"
here is the address:
https://electrum.org/tutorials.html#offline-mpk

[franky1]

https://en.bitcoin.it/wiki/Raw_Transactions
and
https://people.xiph.org/~greg/signdemo.txt

will help you in the right direction

i would also reccomend learning to do raw transactions on testnet first until you do it right as many peeople have shown to not think about transation fee's or 'change addresses' and ended up having alot of funds send as a fee

[ruthless09]

1 - convert your private key into your public key and copy your public key onto something that will transfer your public key to an "online computer"

2 - use an online computer to view transactions of the public address/key and to be able to see the unspent inputs of the public key/address

3 - use one of a number of programs/services that can create an unsigned transaction for you

4 - copy the unsigned transaction from step 3 onto a device used in step 1 and copy it back to your offline computer

5 - use your offline computer to sign the transaction in step 4

6 - transfer the now-signed transaction back to your online computer and push it to the network

[Soros Shorts]

1 - convert your private key into your public key and copy your public key onto something that will transfer your public key to an "online computer"

2 - use an online computer to view transactions of the public address/key and to be able to see the unspent inputs of the public key/address

3 - use one of a number of programs/services that can create an unsigned transaction for you

4 - copy the unsigned transaction from step 3 onto a device used in step 1 and copy it back to your offline computer

5 - use your offline computer to sign the transaction in step 4

6 - transfer the now-signed transaction back to your online computer and push it to the network

It would be nice if steps 4 and 6 could be done using QR codes and the built-in cameras most mobile computers have. Using other convenient methods such as USB drives might prove to be risky.

[bluemountain]

1 - convert your private key into your public key and copy your public key onto something that will transfer your public key to an "online computer"

2 - use an online computer to view transactions of the public address/key and to be able to see the unspent inputs of the public key/address

3 - use one of a number of programs/services that can create an unsigned transaction for you

4 - copy the unsigned transaction from step 3 onto a device used in step 1 and copy it back to your offline computer

5 - use your offline computer to sign the transaction in step 4

6 - transfer the now-signed transaction back to your online computer and push it to the network

It would be nice if steps 4 and 6 could be done using QR codes and the built-in cameras most mobile computers have. Using other convenient methods such as USB drives might prove to be risky.

You would probably want to do step 1 with QR codes as well.

My main concern about this however is that most laptops with digital cameras also come with built in wifi which would potentially make it easy for your "offline" computer to accidentally be an "online" computer

[Dabs]

Turn off the wife. I mean, the wifi.

Disable it. Uninstall the driver. No need to physically destroy it, unless you have no other choice.

[bluemountain]

Turn off the wife. I mean, the wifi.

Disable it. Uninstall the driver. No need to physically destroy it, unless you have no other choice.

If you don't physically destroy it then you (assuming you are wearing a tinfoil hat) are risking that the NSA/US government would be able to remotely enable the wifi

[Spendulus]

Private key is converted into public key from one way cryptography thereafter it is used to sign transaction etc etc. Is it possible to create a offline transction?

I mean do all necessary things offline then it would result in some "lengthy random string" which can only be understand and processed by network. Once that lengthy random string is made we can convert into some hash of 32 bytes. Then write it on paper and then decrypt '32 bit hash'  with computer connected to internet to yield "lengthy random string" which can be broadcast to network?

I don't know much about cryptography. But, I think. It is possible. How can I do it to ensure security of my private key?

First, start with a private key that you are the only one who knows.  Test it. 

Pay zero attention to others who assume that you have a private key and it is secure.  Where did it come from?  A wallet someone told you to trust?

It is not hard to make a private key.

[BTCIndia]

Thank you for all the information! I'll try to create offline transaction and if successful will share with community so that other non-technical people can do same.

[Dabs]

If you don't physically destroy it then you (assuming you are wearing a tinfoil hat) are risking that the NSA/US government would be able to remotely enable the wifi

Excuse me. I do not wear a tinfoil hat. I wear a chrome-vanadium-tungsten alloy helmet. Aside from protecting against mind reading devices, it also deflects 7.62x51mm NATO ammunition.

Also, how would they remotely enable the wifi if it's off and has no drivers installed for it?

[RobertDJ]

If you don't physically destroy it then you (assuming you are wearing a tinfoil hat) are risking that the NSA/US government would be able to remotely enable the wifi

Excuse me. I do not wear a tinfoil hat. I wear a chrome-vanadium-tungsten alloy helmet. Aside from protecting against mind reading devices, it also deflects 7.62x51mm NATO ammunition.

Also, how would they remotely enable the wifi if it's off and has no drivers installed for it?

From the New York Times:

While most of the software is inserted by gaining access to computer networks, the N.S.A. has increasingly made use of a secret technology that enables it to enter and alter data in computers even if they are not connected to the Internet, according to N.S.A. documents, computer experts and American officials.

The technology, which the agency has used since at least 2008, relies on a covert channel of radio waves that can be transmitted from tiny circuit boards and USB cards inserted surreptitiously into the computers. In some cases, they are sent to a briefcase-size relay station that intelligence agencies can set up miles away from the target.

The radio frequency technology has helped solve one of the biggest problems facing American intelligence agencies for years: getting into computers that adversaries, and some American partners, have tried to make impervious to spying or cyberattack. In most cases, the radio frequency hardware must be physically inserted by a spy, a manufacturer or an unwitting user.

This is not exactly the same as remotely activating the wifi but has similar affects.

I am not sure how credible their sources are on this story, however if it turns out to be true then the people wearing tinfoil hats may not actually be crazy

[xrobesx]

1 - convert your private key into your public key and copy your public key onto something that will transfer your public key to an "online computer"

2 - use an online computer to view transactions of the public address/key and to be able to see the unspent inputs of the public key/address

3 - use one of a number of programs/services that can create an unsigned transaction for you

4 - copy the unsigned transaction from step 3 onto a device used in step 1 and copy it back to your offline computer

5 - use your offline computer to sign the transaction in step 4

6 - transfer the now-signed transaction back to your online computer and push it to the network

It would be nice if steps 4 and 6 could be done using QR codes and the built-in cameras most mobile computers have. Using other convenient methods such as USB drives might prove to be risky.

check out the app Bither. There is an app for both Android and iOS. When you first open the app it makes you choose hot or cold wallet. It allows you to use 2 phones, one as cold storage, and sign the transactions with qr codes.

[coolmyrig]

it's impossible I think,offline transaction is not easy.

[itsAj]

I never thought there could be an offline transaction because the network has other people that have to confirm the transaction? Interesting information as always from Bitcointalk I never thought this was possible.

[Dabs]

-snip-

The technology, which the agency has used since at least 2008, relies on a covert channel of radio waves that can be transmitted from tiny circuit boards and USB cards inserted surreptitiously into the computers. In some cases, they are sent to a briefcase-size relay station that intelligence agencies can set up miles away from the target.

-snip-

In most cases, the radio frequency hardware must be physically inserted by a spy, a manufacturer or an unwitting user.

-snip-

I am not sure how credible their sources are on this story, however if it turns out to be true then the people wearing tinfoil hats may not actually be crazy

Well, then it's a good idea to stuff your offline machine outside the reaches of any radio waves. Underground. Copper mesh cage. Behind 3 meters of steel reinforced concrete.

Alternatively, you buy computer parts and assemble it yourself. Anyone who has done any type of bitcoin / alt-coin mining knows how to do this: motherboard, ram, cpu, sata hard drive, etc. The NSA would have to insert the evil hardware into raw computer parts that you would not fail to see unless it was microscopic.

The relay station it communicates with, called Nightstand, fits in an oversize briefcase, and the system can attack a computer “from as far away as eight miles under ideal environmental conditions.”

Make the environmental conditions not ideal. You wrap your little offline computer in tinfoil, or lead or some other heavy metal, I don't know how anything can get anything from it farther than 8 inches.

[bluemountain]

If you don't physically destroy it then you (assuming you are wearing a tinfoil hat) are risking that the NSA/US government would be able to remotely enable the wifi

Excuse me. I do not wear a tinfoil hat. I wear a chrome-vanadium-tungsten alloy helmet. Aside from protecting against mind reading devices, it also deflects 7.62x51mm NATO ammunition.

Also, how would they remotely enable the wifi if it's off and has no drivers installed for it?

As posted above it has been rumored the NSA can remotely "dial into" manufactured computers from miles away. While tinfoil or other heavy metals would work, this is not always easy with mobile computers (laptops, netbooks, tablets, smartphones). IMO it would also be not feasible for most people to house their computer underground as you would need to own actual land and have the ability to "dig" into your land

[Dabs]

It depends on your use case.

If you are just storing less than a hundred or maybe even a couple thousand bitcoins, then just secure it as best you can where you are. The NSA is not interested in your play money when it costs them more to get it.

If you are transacting with tens of thousands or hundreds of thousands of bitcoins, then you better have those 1 foot thick steel walls, little mountains, underground bunkers and other stuff.

For everyone in between, a safe or vault will be enough.


Real life analogy: I am a private citizen so I carry a single 1911 with 2 extra magazines with me, for daily usage. Only when I'm out on a mission do I carry an M4 with grenade launcher or other tools as needed. I drive an unarmored sedan most of the time. The tank stays at the base.

[TinaK]

1 - convert your private key into your public key and copy your public key onto something that will transfer your public key to an "online computer"

2 - use an online computer to view transactions of the public address/key and to be able to see the unspent inputs of the public key/address

3 - use one of a number of programs/services that can create an unsigned transaction for you

4 - copy the unsigned transaction from step 3 onto a device used in step 1 and copy it back to your offline computer

5 - use your offline computer to sign the transaction in step 4

6 - transfer the now-signed transaction back to your online computer and push it to the network

It would be nice if steps 4 and 6 could be done using QR codes and the built-in cameras most mobile computers have. Using other convenient methods such as USB drives might prove to be risky.

You would probably want to do step 1 with QR codes as well.

My main concern about this however is that most laptops with digital cameras also come with built in wifi which would potentially make it easy for your "offline" computer to accidentally be an "online" computer

any alternative solutions?

[Meuh6879]

1) buy a new laptop (netbook, under the 250 USD)
2) install bitcoin core
3) do transactions
4) don't use this netbook to do others things




that's all.




price : 1 BTC.