How to Generate a signed BTC transaction using Electrum and Trezor

[krogothmanhattan]

   I always felt uncomfortable carrying any large amounts of Bitcoin on my cellphone hot wallet when I am in need to carry it with me in the event of any purchases in person. SO that being said I was made aware of a very safe way to not to have the BTC on your phone but still be able to send it to the other persons address once needed.

  What I will show you in the following steps is a way to forge or CREATE a bitcoin transaction of x amount and have it forged to the address given prior to the meet.You can also have the BTC sent to your cell phone hot wallet and then from there you can send wherever you want to send it.

  So if I ever need to send a large chunk of BTC in person, I'd probably forge the transaction before at my place but only broadcast it in person.

  We will be using Electrum and Trezor to accomplish this forged BTC transaction and the output will be a raw Hex data which later I will show you how to transmit on blockchain once needed.


   Step 1

    Download Electrum https://electrum.org/#download
    Verify the the download
    If you do not know the verification steps then please read this article: https://bitzuma.com/posts/how-to-verify-an-electrum-download-on-windows/
    Warning: Do not install the downloaded exe file without verifying the signature. It may risk losing your Bitcoins



    Step 2

    Once installed click on new wallet and this window will pop up. I labeled my new wallet Trezor2

   



     Step 3

     Click on the standard wallet option

     



     Step 4

      Click on using a hardware wallet

     



      Step 5
   
      It will ask you to select a device on your Trezor. I selected the Legacy account as follows.

     



      Step 6

      Your Trezor passcode will pop up..Enter your password and continue..

     



      Step 7

      Since I have a legacy Trezor account I selected legacy from the following options..

     



      Step 8

      The following is self explanatory....I chose to not encrypt.

     



     Step 9

      Electrum will work with your Trezor to create addresses or copy the public addresses onto your PC.

     



      Step 10

      Once is all said and done the folliwng wallet window will open up.

     



     Step 11

      On the top tab click on send and the following screen will come into play.

       Enter the public address where you want to send the Bitcoin to and the amount.

     



      Step 12

      DO NOT hit the send button but rather the preview button as follows...

     



      Step 13

      A new window will come up and show as follows..Click on SIGN now...

     



     Step 14

     Once you click the sign button...you will see a small popup window saying SIGNING TRANSACTION as follows..

     


     
      Step 15

     Your Trezor popup for password will come up to confirm all of this.

       


       
      Step 16

      Now Trezor will ask you to verify and confirm the transaction...

     

      Step 17



     Once completed you will now click on copy as follows..

     



     Step 18

     What you just copied is a raw hex data that will look as follows...

     


        Step 19

       To confirm your raw data is sending to the right Bitcoin address click on decode raw data button as per below

       

         Step 20

         Paste your raw data in the box as per below and then click DECODE TRANSACTION. What you will see is as follows...

         I circled where you should see the BTC address where your Bitcoin will be sent to.

         



    Step 21

     You can now carry this at your leisure knowing that your btc is safe until you broadcast it. Once you do it will goto the address of your choice. If you ever lose the data your btc will remain in your Trezor wallet! So you can never ever lose it due to theft or hacking on your cell phone!!



     Step 22

      Once ready to transmit on blockchain go here and paste in TRANSACTION HEX and then BROADCAST TRANSACTION

      https://live.blockcypher.com/btc/pushtx/


Its that simple!  Cheers!!   

   Thankyou Yogg for showing me the path to enlightenment!

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[krogothmanhattan]

Reserved

[BitcoinGirl.Club]

   Install Electrum https://electrum.org/#download


  

You missed some important information to add about verifying the downloaded file, may be add file lines of a link of the verify download page. This is very important before installing the wallet. By the way, very good tutorial. This will help a lot of users.

Thank you.

Edit: Ok here is the link for you: https://bitzuma.com/posts/how-to-verify-an-electrum-download-on-windows/

I hope this helps

[krogothmanhattan]

   Install Electrum https://electrum.org/#download


  

You missed some important information to add about verifying the downloaded file, may be add file lines of a link of the verify download page. This is very important before installing the wallet. By the way, very good tutorial. This will help a lot of users.

Thank you.

Edit: Ok here is the link for you: https://bitzuma.com/posts/how-to-verify-an-electrum-download-on-windows/

I hope this helps

Thankyou. The link is the official electrum website. Why is that a problem or am I misunderstanding you? Please explain. In the meanwhile will place the main home page as follows..  https://electrum.org/#home  If its coming from Electrums website I am sure the file will not be an issue.

[TryNinja]

Thankyou. The link is the official electrum website. Why is that a problem or am I misunderstanding you? Please explain. In the meanwhile will place the main home page as follows..  https://electrum.org/#home  If its coming from Electrums website I am sure the file will not be an issue.

Verifying the files signatures should be a mandatory step when downloading Electrum. There are many reasons why someone could end up in the wrong website or trusting a phishing email/message. Let’s not forget the last vulnerability where Electrum was showing fake “please update” messages leading to an infected wallet.

Since it was coming from the legit wallet, people fell for it. But if they had the habit of verifying the signatures, they would know that something wasn’t right. Let’s not be lazy with our security; always double check your files.

[BitcoinGirl.Club]

Thankyou. The link is the official electrum website. Why is that a problem or am I misunderstanding you? Please explain. In the meanwhile will place the main home page as follows..  https://electrum.org/#home  If its coming from Electrums website I am sure the file will not be an issue.

You already had your answer here https://bitcointalk.org/index.php?topic=5106013.msg49582538#msg49582538
And I am sure this should be enough to explain.

Thank you.

[krogothmanhattan]

Thankyou. The link is the official electrum website. Why is that a problem or am I misunderstanding you? Please explain. In the meanwhile will place the main home page as follows..  https://electrum.org/#home  If its coming from Electrums website I am sure the file will not be an issue.

You already had your answer here https://bitcointalk.org/index.php?topic=5106013.msg49582538#msg49582538
And I am sure this should be enough to explain.

Thank you.

I see all your points. Very good ones. I updated accordingly and thanks again for the enlightenment..

If I missed anything..please let me know...cheers

[BitcoinGirl.Club]

Step 1

    Install Electrum and verify as https://bitzuma.com/posts/how-to-verify-an-electrum-download-on-windows/

   
https://electrum.org/#home
  

May I help you to rewrite the section?


Step 1
    Download Electrum https://electrum.org/#download
    Verify the the download
    If you do not know the verification steps then please read this article: https://bitzuma.com/posts/how-to-verify-an-electrum-download-on-windows/
    Warning: Do not install the downloaded exe file without verifying the signature. It may risk losing your bitcoins

Code:

[b]Step 1[/b]
    Download Electrum https://electrum.org/#download
    Verify the the download
    If you do not know the verification steps then please read this article: https://bitzuma.com/posts/how-to-verify-an-electrum-download-on-windows/ 
    [color=red]Warning[/color]: Do not install the downloaded exe file without verifying the signature. It may risk losing your[url=https://bitcointalk.org/index.php?topic=5101715.msg49401725#msg49401725] [u]bitcoins[/u][/url]

Hope it helps 🙂

Thank you.

[krogothmanhattan]

Step 1

    Install Electrum and verify as https://bitzuma.com/posts/how-to-verify-an-electrum-download-on-windows/

   
https://electrum.org/#home
  

May I help you to rewrite the section?


Step 1
    Download Electrum https://electrum.org/#download
    Verify the the download
    If you do not know the verification steps then please read this article: https://bitzuma.com/posts/how-to-verify-an-electrum-download-on-windows/
    Warning: Do not install the downloaded exe file without verifying the signature. It may risk losing your bitcoins

Code:

[b]Step 1[/b]
    Download Electrum https://electrum.org/#download
    Verify the the download
    If you do not know the verification steps then please read this article: https://bitzuma.com/posts/how-to-verify-an-electrum-download-on-windows/ 
    [color=red]Warning[/color]: Do not install the downloaded exe file without verifying the signature. It may risk losing your[url=https://bitcointalk.org/index.php?topic=5101715.msg49401725#msg49401725] [u]bitcoins[/u][/url]

Hope it helps 🙂

Thank you.

Updated and of course. Thankyou!

[asche]

Very good tutorial.

Of course this applies the same way if you want to sign your transactions on an offline/airgapped machine and broadcast them later from a possibly compromised device.

[Rath_]

The seventh step lacks information on adding any other account than the default one. Each account in the receive tab in TREZOR web interface displays a BIP32 path which needs to be typed in during that step.



Each account in Electrum will be saved in a separate wallet file.

[krogothmanhattan]

One of the tings I wanted to attempt on doing this was to do it all OFFLINE!

I had started a thread because of issues I can encountered here>>https://bitcointalk.org/index.php?topic=5094605.msg49587834#msg49587834

But I had no luck in doing it or was todl it cannot be done.

Well, a forum member pointed me to this thread here according to the instructions it can be done

 https://www.reddit.com/r/Bitcoin/comments/6kek57/question_trezor_on_offline_computer/

    I will need to find the time to try it again someday in the steps they mention.

   Has anyone had any first hand experience of this? If so kindly share it here or in my other thread as stated above.  

   Thankyou

[krogothmanhattan]

The seventh step lacks information on adding any other account than the default one. Each account in the receive tab in TREZOR web interface displays a BIP32 path which needs to be typed in during that step.



Each account in Electrum will be saved in a separate wallet file.

 Good point but I am just dealing with one Trezor..one account in my case. Still good to know for the person who has multiple accounts 

[Rath_]

Good point but I am just dealing with one Trezor..one account in my case. Still good to know for the person who has multiple accounts

It looks like you have misunderstood me. I am not talking about using multiple TREZOR devices to sign a transaction. TREZOR allows you to create separate accounts which have a different Public Key derived from your Master Public Key. This increases your privacy since it helps you not to mix certain coins, but it's less advanced than Electrum's built-in coin control which can be also used with any TREZOR device. You can generate only up to 20 accounts per passphrase due to performance issues.

[krogothmanhattan]

Good point but I am just dealing with one Trezor..one account in my case. Still good to know for the person who has multiple accounts

It looks like you have misunderstood me. I am not talking about using multiple TREZOR devices to sign a transaction. TREZOR allows you to create separate accounts which have a different Public Key derived from your Master Public Key. This help you to increase your privacy since it helps you not to mix certain coins, but it's less advanced than Electrum's built-in coin control which can be also used with any TREZOR device. You can generate only up to 20 accounts per passphrase due to performance issues.

  That is good to know..Thankyou.

[HCP]

One of the tings I wanted to attempt on doing this was to do it all OFFLINE!

Has anyone had any first hand experience of this? If so kindly share it here or in my other thread as stated above.  

I can't say that I've done it offline as such, but I have certainly used python-trezor to interact with a Trezor device.

So, I tried disconnecting my WiFi, and unfortunately, the example of signing a transaction shown at: https://github.com/trezor/python-trezor/blob/master/docs/EXAMPLES.rst does not work offline. As, if you're offline there is no way for it to find the transaction info necessary to complete the creation of the transaction

Given that it is an open-source library, it should theoretically be possible to modify the python-trezor code so that you could pass in the appropriate transaction information (ie. raw hex) so that it could piece together all the information without needing to connect to the Trezor API...

However, as has already been mentioned a few times, attempting to use a Trezor (or most of the common hardware wallets for that matter) offline is problematic as they all seem to rely on online APIs to retrieve information.

Mainly because the design philosophy of the hardware wallet is that it doesn't need to be used offline to be secure.

[pooya87]

a couple of thoughts:
- is "forge" the correct word? to forge something has the meaning of "faking it" and you are not "faking" anything here. you are creating a real transaction here and don't broadcast it, that's all.

- there is a big problem with this specially when you talk about wanting to spend it. because price is volatile if you create a transaction with X amount at home and then go out, by the time you reach your destination your X may be worth higher or lower than the initial amount you create it at. you can make bigger transactions but then the merchant would have to create a new transaction paying you back the difference. and also you don't know the address of the merchant specially if they are following guidelines and create a new address for every transaction so it is impossible to create a transaction at home!

[HCP]

a couple of thoughts:
- is "forge" the correct word? to forge something has the meaning of "faking it" and you are not "faking" anything here. you are creating a real transaction here and don't broadcast it, that's all.

That is one meaning... forge can also mean "to create". But yeah, it probably isn't the best word to use, especially when talking about things that require signatures etc

forge1
Dictionary result for forge
/fɔːdʒ/Submit
verb
verb: forge; 3rd person present: forges; past tense: forged; past participle: forged; gerund or present participle: forging
1. make or shape (a metal object) by heating it in a fire or furnace and hammering it.
"he forged a great suit of black armour"
synonyms:   hammer out, beat into shape, found, cast, mould, model; More
2. create (something) strong, enduring, or successful.
"the two women forged a close bond"
synonyms:   build, build up, construct, form, create, establish, set up, put together
"they forged a partnership with city government"
3. produce a fraudulent copy or imitation of (a document, signature, banknote, or work of art).
"the signature on the cheque was forged"
synonyms:   fake, falsify, counterfeit, copy fraudulently, copy, imitate, reproduce, replicate, simulate; More
antonyms:   genuine

- there is a big problem with this specially when you talk about wanting to spend it. because price is volatile if you create a transaction with X amount at home and then go out, by the time you reach your destination your X may be worth higher or lower than the initial amount you create it at.

This is a very valid point tho...

[krogothmanhattan]

- there is a big problem with this specially when you talk about wanting to spend it. because price is volatile if you create a transaction with X amount at home and then go out, by the time you reach your destination your X may be worth higher or lower than the initial amount you create it at. you can make bigger transactions but then the merchant would have to create a new transaction paying you back the difference. and also you don't know the address of the merchant specially if they are following guidelines and create a new address for every transaction so it is impossible to create a transaction at home!

   You make a good point however...in the physical crypto world, once a price is predetermined and agreed upon in BTC that is what shall be set in stone..regardless what happens with the FIAT value of BTC. So upon the meet, the agreed upon x amount of BTC shall be delivered. We do not go in FIAT value price but BTC amount. I do anyway..Cheers
 

[bigtimespaghetti]

nice and concise tutorial krogo, thanks for the guide.