A related question:

What is the seed for the pseudo random number generator which creates the Electrum-seed?
Under normal circumstances I would just use the system time. But this would be a very bad idea here because then any attacker could just brute force over all time stamps (which are in seconds or milliseconds) of some day in the past and check for the generated seeds whether they are used, isn't it?
So from where comes the seed for the seed?

(I haven't looked into the code because I assume this would be too much effort for me to understand.)

Like already said, it is possible. In my case, my fault was that I did not import the MPK to my online wallet but only one public key...
For more detailed instructions look here https://github.com/spesmilo/electrum/issues/2033

I have a galaxy ace 2 with  768 MB of RAM and Android version 4.1.2. And Electrum is working on it.

@unamis Indeed, I imported only a BTC address because I thought it would be sufficient. With the imported MPK there is the sign-button which I searched before. Now, everything works fine.
For all who want to know how it's done: via the link of unamis is a good explanation.

I have created an offline wallet on an old phone.

I can create an unsigned transaction with the corresponding watch-only wallet and show it as a qr-code so it can be read by the offline phone.
With the offline wallet I go to "send" and read the qr-code (the unsigned tx). Then I can see the unsigned tx on the offline phone (as an info) but i cannot sign it or do anything useful with it (despite showing it as a qr-code again)...

So how can I sign the tx and give the signed tx back to the watch-only wallet in order to transmit it to the network?

Hello,

neither I am an expert in bitcoin/Electrum nor have I ever traded/bougt bitcoins but I plan to...
For that I would like to make an offline wallet (or "cold storage" how it is called by Electrum) on an Android phone. And a watch-only-wallet on another phone or computer.
So here some questions:

1.) Is that possible with the Android version? I can't find any "import (unsigned) transaction", "sign" or "export (signed) transaction" buttons. I couldn't try it because I have no bitcoins yet, so I can't create any transaction.

2.) When I create a wallet I have to type in a 6 digit pin (which is the encryption passphrase for the private key(s)/seed, right?). Is there any possibility to choose any alpha-numeric "pin" with any length? I would really prefer a longer, not-only-digts - passphrase. (This was already asked in this thread but I don't really understandd the answer...)

3.) I think there is a minor bug in the app: I have to tap three times the upper right menu in order to open it (on two smartphones, one with Jelly Bean the other with Marshmallow).

4.) (just for interest): What is the seed for the seed?  The "Electrum seed" is just a 128 bit (pseudo) random number... but what is the seed for that number? Is it the time on the phone?

Thanks for the hints and explanation.

Obviously, I want a watch-only wallet

bitcoin.org says, there is also an Android version of Electrum. I'll take a look at it!

Hello,

I'm new here and this is my first contribution here.
I think about buying some (or one) bitcoins but until now i have never done anything with bitcoins yet. So please forgive me if I make a false assumption, error in reasoning or something like that =)

I would like to have a bitcoin wallet which lies on a (perhaps old one but especially for that reason) smartphone. This smartphone shall, for security reasons, never be online. So in order to make transactions I have to create a transaction order (I'm sure there's a better word for that but... I don't know it...) with the offline phone and transfer this order (ideally with a QR code) to some online device that forwards this order to the bitcoin network.

Is there a bitcoin wallet (android?) that can create such transaction order QR codes? And is there a program (android/windows?) that can read and forward these transaction orders? Additionally, it would be very nice if the offline wallet provides encryption so that the private key is encrypted by a passphrase.

I really would like to do it that way because I don't want to entrust my bitcoins to some online hoster. I want to store my bitcoins by myself SECURELY.

(I know there are some hardware wallets... that would be plan B =))

Thanks for your help!
Lumpi