21 Bitcoin Computer - the Macintosh of Bitcoin

It looks like the 21 Bitcoin Computer has began shipping recently for $400 apiece. Moreover, we also got a few extra bits of information from the 21.co website about some features and solutions of the machine and the ecosystem in general. Since guessing the business model of 21 Inc seems to be everyone's favourite activity for about half a year now, lets not waste any more time and dig right in.

The hardware

First of all, we've got some photos of the actual machine. The packaging looks good, the mining component of the device looks sleek and elegant, while the actual computer is a standard Raspberry Pi 2 (according to the FAQ). Strange it doesn't come in a case, especially given that even their setup steps seem to be aware that this might cause some problems:

The 21 Computer's mining chip appears to have the following specs:

  • 0.16 Joules per Gigahash
  • 50 Gigahashes per second
At the moment there don't appear to be any upgrade / swap options for the machine.

This seems to put it in the same category as Antminer U3 Batch 2 - currently selling for $20 and clocking in at 63GH/s. The energy efficiency is rather odd - comparing it to existing solutions, it would be at roughly 6250 MHash/J, while the top performer, AntMiner S7 performs at 4000 MHash/J. This would seem to suggest the chip is underclocked to be more efficient.

This is a little ironic coming from a company that wants to put mining chips into mobile devices - if you're worried about the power efficiency of a device that runs straight from a power adapter, and yet you want to include extra power hungry hardware in devices that run off battery power...

At any rate, this puts the value of the whole package at under $100 (with the Rapsberry Pi 2 along with all the extras selling for about $70 at the moment). But, the hardware isn't everything, so lets look at what else we get with the 21 Computer.

The Software

It looks like the 21Inc's software is quite packed with features. The CLI looks exhaustive, you can run a full Bitcoin node, you have your wallet, etc. We have some reports of people running things like the Open Bazaar project on the device just fine.

All in all, it looks like the software is the meat of the package. I've seen a number of people being interested in the software component more so than the whole package itself. Luckily, it seems that one can get the whole open source software without having to buy the 21 Computer:

> curl https://install.21.co/bitcoin-computer/install.sh | sudo bash

Beyond that, I personally don't have much else to say about the software in general. It looks to be delivering on what it's promising in one neat package.

The Rest

Beyond the hardware and software, it looks like (at least for now during the launch week) 21Inc has some responsive consumer service, which is great to know. If some people get into Bitcoin because of this computer, this can be a very valuable service to make sure they stay interested in the service.

The 21 website has a few interesting tutorials on what could be done with the software. Moreover, with the $200 tutorial bounty, we can expect to see more articles popping up over time.

Beyond that, we come into some more interesting nuggets of what could either be something really insignificant in the future, or perhaps will end up as a starting point for something more insidious...

The Quirky


It seemed that from the very beginning, 21Inc was aiming to sell everyone on the idea of combining Bitcoin mining with Internet of Things. However, as I discussed almost half a year ago exactly, this makes no economic sense whatsoever. Mining dust wouldn't even cover for the transaction fees, much less amount to anything useful.

However, in their tutorial on micropayments, we can see that probably the encouraged method of transferring money between individuals won't be the Bitcoin network itself, but the so called "BitTransfers", which looks like a fancy way of saying "shared ewallet transfers". In other words, 21Inc is building itself up to be something like CoinBase for the IoT world - settling peer-to-peer transactions using its centralized database.


Now, to load the wallet, one would of course mine the coins using the 21 Computer. Even in this area could be spruced up with some marketing talk, as we go into the mining tutorial and "buffered pool mining". 

We start with a time lesson talking about transitioning between CPU mining into pool mining when one couldn't realistically mine a block by themselves. Pooled mining allowed one to reduce the reward variance (without the pool, you either got a whole block and 50BTC, or no block and no reward, while pooled mining allowed you to get a fraction of the reward, but at a more regular pace). 

Afterwards, we seem to get a vision of what 21Inc wants to sell as the vision for its computers - "redecentralizing Bitcoin" by the use of "millions of mining chips worldwide each generate a small stream of bitcoin" as they believe the ASIC chip development will start following the Moore's law in the near future.

However, since the default way (and possibly the only way without modifying the software) to mine on the 21 Computer is to connect to the 21Inc's pool and receive the dust rewards in your 21 shared ewallet, it's not really a decentralization of mining as it is adding another central server to the equation.

Perhaps if we would instead see P2Pool on the device we could call it an effort in the right direction, but then you wouldn't be able to solve the mining variance problem very well, nor would you lock people into your walled garden of an ecosystem.

In the next section we get another new buzzword - "Buffered Pool Mining". You see, 21Inc believes that if you're mining in a pool, you will have to wait:
  • For the pool to mine a block before you get paid
  • To mine enough coins to reach the minimum withdrawal threshold
  • For the block to mature over 100 confirmations before you can get paid
  • To earn bitcoins before you can spend them again if you run out

Instead, 21Inc essentially combines its shared ewallet with the circa 2011 BitPenny's idea of Pay-per-share. As described in the Bitcoin Wiki:

The Pay-per-Share (PPS) approach, first described by BitPenny, is to offer an instant flat payout for each share that is solved. The payout is offered from the pool's existing balance and can therefore be withdrawn immediately, without waiting for a block to be solved or confirmed. The possibility of cheating the miners by the pool operator and by timing attacks is thus completely eliminated. 
This method results in the least possible variance for miners while transferring all risk to the pool operator. The resulting possibility of loss for the server is offset by setting a payout lower than the full expected value.

I wonder how hardened is the 21 mining pool against what an attacker with a state-of-the-art mining rig could throw at it...

But we also get one more interesting feature, which is essentially Bitcoin, lets say, nanolending:

Finally, you do not need to send N hashes to the server before getting N hashes worth of mined bitcoin. That is, by invoking 21 mine your 21 Bitcoin Computer can receive bitcoin in advance of future mining at the expense of a small asymptotic slowdown in the rate of bitcoin streamed to your device.

Which considering the price tag of the machine is still rather amusing.

We conclude the tutorial with:

The basic idea is that buffered pool mining is a new way of getting bitcoin: not by buying huge quantities slowly for investment purposes on an exchange, but by mining tiny quantities rapidly for programming purposes at the command line, rate-limited by a mining chip.

I guess someone forgot the middle-ground of being able to buy a small amount of BTC, for example by phone, getting small amounts of coins for free (through facets or by signing up to various wallets), or if you're really a developer, using TestNet Bitcoins.

Anything else?

As someone that frequents the Bitcoin-related subreddits, I noticed a large amount of submissions about the device recently. That's to be expected when a new, big product launches and everyone gets their hands on it. However, some of the submissions and discussion appears to be somewhat astroturfed. Submissions titled "Whoa" that aren't some Shiba Inu memes generally don't do very well on a crypto subreddit. Cynical quips usually stick better, you rarely see people talking in bold (1, 2), and hardware is rarely inspirationally compared to some major milestones in commercial computing. Even the self-post appear a bit defensive (1, 2). My money would be on at least some of the sentiment being not entirely as grassroots as it might appear in the first place...


Coming back to the title of my post - 21 Bitcoin Computer to me looks like a Macintosh Computer for Bitcoin - an overpriced, underpowered piece of hardware coupled with some decent software. It appears to be building the roots of a walled garden of closed-loop wallets and related ecosystems. If you're a developer, you can do better, both in terms of mining performance, computing speed and price for a throwaway machine for testing. Their software and related articles appear to be the main piece of value added.

For $400, even for a "dev kit" as it's sometimes advertised, I would still rather buy some BTC (by "buying huge quantities slowly for investment purposes on an exchange" - which would still be a smaller investment than the machine) instead of committing to mining. But perhaps it's like some random comment said on Reddit - "the investment will get you to commit to using it".

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