[Solved]Electrum on Android: How to create a SIGNED raw transaction please?

[Saint-loup]

Hello
I'm able to create an unsigned raw transaction with Android Electrum, but I don't find how to create a signed raw transaction  
Does anyone know how to do that if it's possible?
Thank you very much.

[Rath_]

I'm able to create an unsigned raw transaction with Android Electrum, but I don't find how to create a signed raw transaction Does anyone know how to do that if it's possible?

Prepare an unsigned transaction on your computer and display it as a QR code or create a watch-only wallet using your Master Public Key (click on the wallet name to obtain it), prepare the transaction and copy it by clicking on the QR code icon and selecting 'Copy to clipboard'. Scan the QR code by tapping on the camera icon in the 'Send' tab or paste the unsigned transaction. Review the transaction and select 'Options -> Sign'. Once you have signed the transaction, tap on the QR icon in the middle and then press 'Copy to clipboard'.

[jackg]

I'm able to create an unsigned raw transaction with Android Electrum, but I don't find how to create a signed raw transaction  

That's an interesting question, I'm not sure you can but I'll have a bit of a test.

I know you can do it by making two 1 of 2 multisig wallets but I'm not sure if youc an do it with a regular one.

[Rath_]

That's an interesting question, I'm not sure you can but I'll have a bit of a test.

Yes, you can. Read the post above for two possible options. It isn't as easy as if you were doing it on a desktop version of Electrum.

[Saint-loup]

I'm able to create an unsigned raw transaction with Android Electrum, but I don't find how to create a signed raw transaction Does anyone know how to do that if it's possible?

Prepare an unsigned transaction on your computer and display it as a QR code or create a watch-only wallet using your Master Public Key (click on the wallet name to obtain it), prepare the transaction and copy it by clicking on the QR code icon and selecting 'Copy to clipboard'. Scan the QR code by tapping on the camera icon in the 'Send' tab or paste the unsigned transaction. Review the transaction and select 'Options -> Sign'. Once you have signed the transaction, tap on the QR icon in the middle and then press 'Copy to clipboard'.

Hello BitCryptex
Thank you for your answer.
I don't want to use a computer, I would like a solution working with only a smartphone.
So when(on which screen) I must "paste" the unsigned transaction please?

[Rath_]

So when(on which screen) I must "paste" it please?

Once you prepare your transaction using the watch-only wallet and copy it, switch to the default wallet. In the 'Send' tab, there are a few buttons. 'Paste' is directly above 'Pay'.

[BitMaxz]

@BitCryptex

It seems that it only works on Electrum to Electrum wallet I tried the QR code generated from coinb.in as unsign raw transaction and use their qr code but when I scanned it with Electrum in mobile shows unable to decode.

But the Electrum PC to Electrum mobile works fine to me after you sign it on your mobile you can copy the raw transaction and save it as txt then transfer it to PC to broadcast.

So I think there is no difference in signing transaction in two mobile phones if the watch-only wallet can show a QR code after you make unsigned transaction you can scan it from another mobile phone where you can sign the transaction.
It is just the same as the method by BitCryptex. It is likely the same as an airgap wallet. You can get the raw transaction under QR code and paste it to your another wallet in the same device it works to me.

[Rath_]

It seems that it only works on Electrum to Electrum wallet I tried the QR code generated from coinb.in as unsign raw transaction and use their qr code but when I scanned it with Electrum in mobile shows unable to decode.

That's because Electrum uses base43 in order to make QR codes smaller; it looks like the client also expects this kind of encoded data.

So I think there is no difference in signing transaction in two mobile phones if the watch-only wallet can show a QR code after you make unsigned transaction you can scan it from another mobile phone where you can sign the transaction.

There is no need to use two separate phones. Electrum on Android allows users to switch between wallets (tap on the three dots in the top-right corner). When you open a QR code, you can also copy the text to clipboard.

[Saint-loup]

It seems that it only works on Electrum to Electrum wallet I tried the QR code generated from coinb.in as unsign raw transaction and use their qr code but when I scanned it with Electrum in mobile shows unable to decode.

That's because Electrum uses base43 in order to make QR codes smaller; it looks like the client also expects this kind of encoded data.

So I think there is no difference in signing transaction in two mobile phones if the watch-only wallet can show a QR code after you make unsigned transaction you can scan it from another mobile phone where you can sign the transaction.

There is no need to use two separate phones. Electrum on Android allows users to switch between wallets (tap on the three dots in the top-right corner). When you open a QR code, you can also copy the text to clipboard.

Thank you very much BitCryptex, I can confirm it worked very well with only one smartphone.
You just need a watch only wallet to create an unsigned raw tx and a normal one to sign the unsigned raw tx pasted.

But I have another question : is there a website that can decode this Qr code in text? So the "receiver" who took a picture of my Qr code can easily decode it and broadcast it without installing Electrum...
Or I must send to him the text of the raw tx by SMS?

[TryNinja]

But I have another question : is there a website that can decode this Qr code in text? So the "receiver" who took a picture of my Qr code can easily decode it and broadcast it without installing Electrum...

Yes.

This one for example: https://zxing.org/w/decode.jspx

And if the QR contains the already signed tx and you only need to broadcast it, then there is no security risk on using a third-party website like this one.

[Rath_]

But I have another question : is there a website that can decode this Qr code in text? So the "receiver" who took a picture of my Qr code can easily decode it and broadcast it without installing Electrum...

You can either send the QR code and ask the other person to decode its contents using this website or simply send the copied signed transaction to them ('Copy to clipboard' should be available once you open the QR code). Electrum encodes the (un)signed transaction only if you select the QR code.

[Saint-loup]

But I have another question : is there a website that can decode this Qr code in text? So the "receiver" who took a picture of my Qr code can easily decode it and broadcast it without installing Electrum...

Yes.

This one for example: https://zxing.org/w/decode.jspx

And if the QR contains the already signed tx and you only need to broadcast it, then there is no security risk on using a third-party website like this one.

Yes I know this website and I already tried it but I get a weird string which is not even in base64, I don't know in which format it is and if I can convert it in hexadecimal format.
I get this kind of string :
64XF-8+PM7IUWCPS$XA3$S0SGDXXHYH36DQN/KL3FX.Q.H$HE0N.OA.-K50CDLBO2.40/HZEM-L3*EX58 ....

[TryNinja]

Yes I know this website and I already tried it but I get a weird string which is not even in base64, I don't know in which format it is and if I can convert it in hexadecimal format

Did you try getting the weird string and putting it in the website BitCryptex linked above?

http://electrum43.org/

[Saint-loup]

Yes I know this website and I already tried it but I get a weird string which is not even in base64, I don't know in which format it is and if I can convert it in hexadecimal format

Did you try getting the weird string and putting it in the website BitCryptex linked above?

http://electrum43.org/

Yes you're right it worked fine! I got an hexadecimal string and I've been able to broadcast it!
Thank you very much TryNinja and BitCryptex