Topic: bitcoincard.org - page 8. (Read 29284 times)

An offline device can create and sign a transaction, it cannot validate it.  However, (in theory, don't know about this device yet) any disconnected device with local copies of it's inputs could also keep the merkle trees that show where those input transactions fit into the blockchain.  This is about as close to an offline validation as it likely possible.


First the 'gateway' is just another mesh radio connected to the Internet, there is no reason to expect that the gateway itself would be a bitcoin node.  A counter-party to a change based transaction needs to be able to see that the previous transaction fits into a block, otherwise the next transaction is indistingishable from a double spend attempt.  This would be possible if the counter-party were a connected full node & the prior transaction made it back to the internet by another path,but such an event cannot be assumed.

/watching

Didn't understand this.
AFAICT, this device cannot validate any transaction while offline. It would be a task to the gateway.
And why can't a bitcoincard A send a series of linked-by-change transactions to B, and then B uploads them all to his gateway?

I suspect that I know the tech being presented here, and if I'm correct, the video is likely understating the practical ranges.  I know that I'm guilty of speculation, but I suspect that the mesh tech alluded to is dash7.

http://en.wikipedia.org/wiki/DASH7

Note that Dash7 devices are inherently location aware, in a relative sense; i.e. they know where there are relative to other dash7 devices.  The customer location tracking features mentioned in the video are one of the encentives for vendors to adopt a set of 'dongles', which would (presumedly) be aware of their own positions in an absolute sense (GPS).

Also note that Dash7 devices can have theortical ranges up to 2km, which practially means about 1km; and that it's max data rate is 200kbps.  However, it cannot do both max range and max speed at the same time, so the video's downgrading of the noted ranges might be due to a concern of overpromising or it might be due to the intent of the card designers fixing the data rate at the max and otherwise living with whatever range remains.

Dash7 isn't good for data that streams or large files, but for mesh propogation of bitcoin data it's practially ideal.  Also the ISM band that DAsh7 uses (433Mhz) is a 32nd harmonic of that which NFC uses as a standard, so both techs can coexist on the same tranceiver and share much silicon, making such features cheaper to produce.

There would be a practical limit, but it's one that's hard to predict.  It depends upon the input transactions that the device has in local storage, because it can only make transactions based upon the unspent inputs that it has since last connect.  It's not practically possible for a disconnected device (light or otherwise) to be able to use the change from a previous transaction as an input in a new transaction because all other devices should require that the change transaction have 6 confirms or at least a copy of the block's merkle tree as evidence that it's a valid transaction and not a double spend.  Since the device is disconnected, there is no way for it to have that evidence even if some other device has already forwarded the transaction to the network on it's behalf.  In practice, such a device is going to have to keep a set of seperate transaction inputs of varied sizes in order to make multiple payments between online sessions.

Question: how many p2p transactions can be stored and forwarded for later? If you aren't near a dongle, and other users are creating transactions near you, I assume that each device queues all the tx up until one of them gets near a dongle and spews the info onto the internet. Is there a practical imitation on the number of stored transactions? This assumes that it is a lightweight client, but if it is a full node that would be a bit different too.

I guess that would depend on population density. Though I wonder that since this is very low bandwidth communications, perhaps "dummy nodes" consisting of walletless transceivers couldn't be embedded everywhere from utility poles to business signs to mailboxes, etc.

And the maximum range of the dongle is 100 metres according to the website. Presumably the card-to-card mesh communications will have, if anything, an even shorter range. I can't imagine this working terribly well somehow. Most likely the "mesh" functionality will end up being something that looks good on the spec sheet but isn't actually practical - at least not for Bitcoin payments - and the entire thing will be dependent on the fixed access points to work properly.

I will definitely buy your magazine when it hits the bookstores in Dallas, TX with or without Bitcoin.

Ditto!

FYI that is not a proven feature, it's a video to collect investments for development.

okay so debit card can only be lost or stolen the money can still be spent by a thief and you can hope the bank will refund you. If a green dot card is lost or stolen your completely out of luck.

this card can be lost or stolen. The only other thing you need to worry about is breaking it. I was giving 500BTC as an explain. You would only put as much on the card as you would in your wallet.

@up
you can receive coins too. they showed that in the video sending coins to your friend on the street.

ya 500BTC was a bad amount to pick I figured it would last the month and you would reload it every month but even that is a lot. 20-100BTC would of been a better amount to use.

I just think it is a pity that it's only a device to spend coins. It's not that much better than a good smartphone app in that sense. Ok, much cooler, but functionally similar.
If it only had (1) different addresses per transactions and (2) the possibility to backup the addresses' seed, it would be more than a device to spend btcs, it would be the best device available to store all of your coins, due to its dedicated platform. The likelihood of a malware infecting this device is lower than any other solution we currently have. Add (3) hidden volumes for plausible deniability and you've got the "ultimate bitcoin wallet".

(btw, if 500BTC is your "daily use" which you can easily afford to lose, I envy you )

Rofl. The only way you'll be using any Bitcoin enabled payment device to buy the Bitcoin Magazine in Barnes in Noble is if you're buying it off our website while simply happening to be in Barnes and Noble.

500 BTC is ~$2500.  If my debit card stops working I don't lose $2500 the bank just issues me a new debit card.  Your analogy doesn't make much sense.  If anything you pointed out that without backups it is NOT like a debit card.  It is more like cash and personally I don't carry around $2500 in cash for the exact reasons of loss/theft.

That's awesome! Will I be able to use it at Barnes and Nobles to buy Bitcoin Magazine?

After Iceland I'll be flying to the USA for the next few months to work on it there with other projects as well. The prototype is already available, we're just working out the mass manufacturing. It's basically a money issue at this point. Making something of the magnitude we're planning (50,000 units at $30 a pop) will take about $1million cold and it won't move without $100k down, not to mention the fact that $100k is easily eaten by redesigning UI, debugging, molding, plates, PCBs, etc and any mistakes at the manufacturers. Not to mention marking and advertising budgets to get it into every store in the USA as a payment device.

This shit is big, but it has to be done right. I believe wholeheartedly that Bitcoincard is being done wrong in every way (advertising, branding, marketing, funding, design, technology, infrastructure, etc). We'll gladly let the free market decide though. The kickstarter goes up soon, but everything in this post is completely unofficial and nonbinding.

OK, I see it uses ISM bands. Bluetooth also uses ISM bands, so while it may not be Bluetooth, it seems to be using the same concept.

IF I could get them right now I would take 6 (maybe 15 and try to sell the idea to the rest of my family). BTW Im they posted a new video recently which demonstrated a bitcoin transaction.

I dont see why anyone is complaining about not backing them up or them getting lost. They work exactly like a debit card or one of those green dot cards. You load it with as much money as you need. Every month youd put 500BTC on the card to refill it for daily use. You shouldn't be carrying around your life saving in your pocket! You dont do that with cash or your debit card now, itd be silly to do that with this device.


mattewN when are we getting more information about that bitdex?

PS. Im already upset that it doesnt talk to me all the time like a pokedex

I don't usually post useless and offtopic posts, but... I want one. No, actually I want 2 and I want them NOW !

STFU or delivar. Your choice.