Topic: Tx signing via minimodem (Read 4247 times)

Its not about storrage of keys, its about transfering your unsigned TX from the hot wallet to your cold wallet to get it signed and back without risking the cold wallets machine to get some virus/trojan/etc. the hot wallets machine might have.

I haven't seen the videos, but how much better is that one compared to if I just store my keys as spoken words? Spelled out letters, or in morse code. (Number 1, small L, big U, etc.)

I'm speechless. Very clever. Kudos

While someone is trying to use QR code in a wrong way, I think of this. With the recent discovery of the critical flaws in USB I really hope this could be integrated into bitcoin wallets.

I've seen a few comments about using audio for sending the data to the offline computer and back. It's an idea that appealed to me quite a bit, probably back from my audio days when audio still was analog. Well, anyway, the solution I found to work is using minimodem:
http://www.whence.com/minimodem/
https://github.com/kamalmostafa/minimodem

There are a few videos on the site and that is exactly how it works. It is easy to install as it doesn't have many dependencies. It's in the Ubuntu repos since 12.04
http://packages.ubuntu.com/search?keywords=minimodem&searchon=names&suite=all§ion=all

For lucid there's a version on the author's launchpad site.

I've tried it with both a mic / speaker combination and a straight 3.5mm stereo male-male audio jack cable, you may know these as "Aux" cables. I didn't have any noticeable impedance problems when using the cable. Volume Out and Mic In levels were set to about half of the slider. This can be fine tuned in the audio settings.

Using the -A flag produced noticeably better results than using Pulseaudio (the default). I could tell just from listening that the Pulseaudio signal was distorted at times.

For the baudmode I selected 1200 in this case and it took about a minute to send one way. I think that is on par if not quicker than USB, considering you have to select your file, "safely remove", move the stick, wait for it to appear etc. Of course this depends on the actual transaction size.

I have not played around much more with higher speeds or with the different flags as of yet; a full list is at the man page.

If you are using the mic /speaker combination on a regular basis, it will make it easier if you have two of each to have it bi-directional without moving plugs. And judging from comments of my housemates, you'll probably want to stick them in a soundproofed box