URGENT! How can I safely send bitcoins from my phone?

[9thsky]

I personally play things safe and would do an unsigned transaction (https://electrum.readthedocs.io/en/latest/coldstorage.html) from an airgaped computer, but I have a friend that I got into bitcoin that doesn't have her airgaped computer where we created a cold storage, nor any other device she could use besides her Android. She wants to send bitcoin (electrum) from her phone (which is rooted). What steps could she take to ensure a smooth transaction? Let's assume worst case scenario where her phone is infected with malware.

I'm guessing she would have to go live with her seed (put it in Electrum mobile) to do so, unless there is another way of doing it, like creating an unsigned transaction, from a mobile phone, from 1 device?

The whole sending transaction will probably just last a few seconds.

Greatly appreciate your expertise in this guys!

[BitMaxz]

Rooted phones are unsafe to use online if you want to send BTC from your rooted phone you can make unsigned transactions from https://coinb.in/#newTransaction just paste the BTC address of your wallet.


Once you create an unsigned transaction from coinb.in you can copy the unsigned raw/hex code and transfer it to the rooted phone and import it to Electrum(mobile).

Or if you have the backup seed you can just import it to another device that is not rooted and known clean from any virus/malware. Then you can just send your bitcoin anywhere without thinking about malware.

[9thsky]

Rooted phones are unsafe to use online if you want to send BTC from your rooted phone you can make unsigned transactions from https://coinb.in/#newTransaction just paste the BTC address of your wallet.


Once you create an unsigned transaction from coinb.in you can copy the unsigned raw/hex code and transfer it to the rooted phone and import it to Electrum(mobile).

Or if you have the backup seed you can just import it to another device that is not rooted and known clean from any virus/malware. Then you can just send your bitcoin anywhere without thinking about malware.

Can you walk me through the steps please? How exactly do I do this through coinb.in?

[ranochigo]

If you cannot use any other device other than the Android which is infected with malware, there is no way you can use it without an internet connection and thus the malware will always steal your funds whenever you go online. If your phone is (in the worst case scenario) infected with malware, I can't see any reason why you wouldn't be trying to back up your seeds and important files before resetting the phone completely.

If you do have another computer with a QR code, you can click your wallet and your master public key should be shown. Import that onto an Electrum on your computer as a watchonly wallet. Next, use the desktop Electrum to create a raw transaction, Finalize and export using QR Code. Afterwhich, go back to your phone and in the Send Tab, press scan and you should be able to sign your transaction. Using the desktop Electrum, go to Tools>Load Transaction>From QR Code and you can broadcast using that.

Unless you know exactly how to use Coinb.in and which addresses the funds are located in, you shouldn't use coinb.in. It's tougher to use than most wallet UIs and is more suited for advanced users. Coinb.in also seems to break the raw transaction when copied to Electrum as well.

[BitMaxz]

Can you walk me through the steps please? How exactly do I do this through coinb.in?

It's not hard to make unsigned raw transactions from Coinb.in. Anyway, I'll walk you through check the image below.



Under output ignore the 2nd address if you want to send the whole BTC from your old wallet(which is your friend's rooted phone) to the new wallet.
And take note of the transaction fee make sure to pay enough fee because I have a bad experience before that I accidentally paid a large fee without checking it.
I forgot to mention the inputs tab but as you can see on the image it's all of your combined amount of BTC(Total amount of your BTC)

Then submit it after you set them properly and you will see something like this



That's your raw/hex unsigned transaction now paste it to this tool https://coinb.in/#verify to check if everything is fine. If all are fine now you can transfer the raw/hex to your rooted phone through OTG or any way to transfer without using the internet.

Once you transfer you can signed the transaction and transfer it back to your online machine and broadcast it here https://coinb.in/#broadcast


I hope that you can follow...

[ranochigo]

-snip-

Have you tried signing it with Electrum? Might be just a problem with mine but it won't sign and shows it as signed already.

I don't think CoinB.in would be the best idea. Using Electrum to script raw unsigned transaction is much more convenient as it displays the size of the transaction beforehand for a more accurate fee. Using the master public key in place of individual addresses would help the user to spend all the funds if needed. It also doesn't have a QR code plugin to encode QR codes.

[Abdussamad]

tell her that bitcoin transactions are irreversible. rooted phones are not safe.

consider that she may not be interested in bitcoin and is only saying this to dissuade you. you should take the hint.

[BrewMaster]

https://coinb.in/

you need to double check to make sure if the raw unsigned transaction hex that coinb.in creates is compatible with electrum. i don't know about new versions but last time i tried another tool the result wasn't accepted in electrum to be signed then i found out that electrum expects some extra data in the scriptsig to be able to figure out how to sign it offline that are only defined in electrum itself.

[ranochigo]

you need to double check to make sure if the raw unsigned transaction hex that coinb.in creates is compatible with electrum. i don't know about new versions but last time i tried another tool the result wasn't accepted in electrum to be signed then i found out that electrum expects some extra data in the scriptsig to be able to figure out how to sign it offline that are only defined in electrum itself.

It doesn't, online or not.