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Concerns About Blockchain

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Concerns About Blockchain

Blockchain holds a lot of promise for the software industry, especially in security related fields. But will the technology ever live up to the hype?

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The so-called (and marketing-branded) “blockchain technology” is promised to revolutionize every industry. Anything, they say, will become decentralized, free from middle men or government control. Services will thrive on various installments of the blockchain, and smart contracts will automatically enforce any logic that is related to the particular domain.

I don’t mind having another technological leap (after the internet), and given that I’m technically familiar with the blockchain, I may even be part of it. But I’m not convinced it will happen, and I’m not convinced it’s going to be the next internet.

If we strip the hype, the technology behind Bitcoin is indeed a technical masterpiece. It combines existing techniques (likes hash chains and merkle trees) with a very good proof-of-work based consensus algorithm. And it creates a digital currency, which ontop of being worth billions now, is simply cool.

But will this technology be mass-adopted, and will mass adoption allow it to retain the technological benefits it has?

First, I’d like to nitpick a little bit – if anyone is speaking about “decentralized software” when referring to “the blockchain,” be suspicious. Bitcoin and other peer-to-peer overlay networks are in fact “distributed” (see the pictures here). “Decentralized” means having multiple providers but doesn’t mean each user will be full-featured nodes on the network. This nitpicking is actually part of another argument, but we’ll get to that.

If blockchain-based applications want to reach mass adoption, they have to be user-friendly. I know I’m being captain obvious here (and fortunately some of the people in the area have realized that), but with the current state of the technology, it’s impossible for end users to even get it, let alone use it.

My first serious concern is the need to download the whole blockchain on your machine. When I got my first bitcoin several years ago (when it was still 10 euro), the blockchain was kind of small and I didn’t notice that problem. Nowadays both the Bitcoin and Ethereum blockchains take ages to download. I still haven’t managed to download the Ethereum one – after several bugs and reinstalls of the client, I’m still at 15%. And we are just at the beginning. A user just will not wait for days to download something in order to be able to start using a piece of technology.

I recently proposed downloading snapshots of the blockchain via BitTorrent to be included in the Ethereum protocol itself. I know that snapshots of the Bitcoin blockchain have been distributed that way, but it has been a manual process. If a client can quickly download the huge file up to a recent point, and then only download the latest ones in the the traditional way, starting up may be easier. Of course, the whole chain would have to be verified, but maybe that can be a background process that doesn’t stop you from using whatever is built ontop of the particular blockchain.

But even if such an approach works and is adopted, that would still mean that for every service you’d have to download a separate blockchain. Of course, projects like Ethereum may seem like the “one stop shop” for cool blockchain-based applications, but fragmentation is already happening – there are alt-coins bundled with various services like file storage, DNS, etc. That will not be workable for end-users. And it’s certainly not an option for mobile, which is the dominant client now. If instead of downloading the entire chain, something like consistent hashing is used to distribute the content in small portions among clients, it might be workable. But how will trust work in that case, I don’t know. Maybe it’s possible, maybe not.

And yes, I know that you don’t necessarily have to install a wallet/client in order to make use of a given blockchain – you can just have a cloud-based wallet. Which is fairly convenient, but that gets me to my nitpicking from a few paragraphs above and to may second concern – this effectively turns a distributed system into a decentralized one – a limited number of cloud providers hold most of the data (just as a limited number of miners hold most of the processing power). And then, even though the underlying technology allows for a distributed deployment, we’ll end-up again with simply decentralized or even de-facto centralized, if mergers and acquisitions lead us there (and they probably will). And in order to be able to access our wallets/accounts from multiple devices, we’d use a convenient cloud service where we’d login with our username and password (because the private key is just too technical and hard for regular users). And that seems to defeat the whole idea.

Not only that, but there is an inevitable centralization of decisions (who decides on the size of the block, who has commit rights to the client repository) as well as a hidden centralization of power – how much GPU power do the Chinese mining “farms” control and can they influence the network significantly? And will the average user ever know that or care (as they don’t care that Google is centralized)? I think that overall, distributed technologies will follow the power law, and the majority of data/processing power/decision power will be controlled by a minority of actors. And so our distributed utopia will not happen in the pure form we dream of.

My third concern is incentive. Distributed technologies that have been successful so far have a pretty narrow set of incentives. The internet was promoted by large public institutions, including government agencies and big universitives. BitTorrent was successful mainly because it allowed free movies and songs with 2 clicks of the mouse. And Bitcoin was successful because it offered financial benefits. I’m oversimplifying of course, but “government effort,” “free and easy,” and “source of more money” seem to have been the successful incentives. On the other side of the fence there are dozens of failed distributed technologies. I’ve tried many of them – alternative search engines, alternative file storage, alternative ride-sharings, alternative “internets” even. None have gained traction. Because they are not easier to use than their free competitors and you can’t make money out of them (and no government bothers promoting them).

Will blockchain-based services have sufficient incentives to drive customers? Will centralized competitors just easily crush the distributed alternatives by being cheaper, more-user friendly, having sales departments that can target more than hardcore geeks who have no problem syncing their blockchain via the command line? The utopian slogans seem very cool to idealists and futurists, but don’t sell. “Free from centralized control, full control over your data” – we’d have to go through a long process of cultural change before these things make sense to more than a handful of people.

Speaking of services, often examples include “the sharing economy,” where one stranger offers a service to another stranger. Blockchain technology seems like a good fit here indeed – the services are by nature distributed, why should the technology be centralized? Here comes my fourth concern – identity. While for the cryptocurrencies it’s actually beneficial to be anonymous, for most of the real-world services (i.e. the industries that ought to be revolutionized) this is not an option. You can’t just go in the car of publicKey=5389BC989A342…. “But there are already distributed reputation systems,” you may say. Yes, and they are based on technical, not real-world identities. That doesn’t build trust. I don’t trust that publicKey=5389BC989A342… is the same person that got the high reputation. There may be five people behind that private key. The private key may have been stolen (e.g. in a cloud-provider breach).

The values of companies like Uber and Airbnb is that they serve as trust brokers. They verify and vouch for their drivers and hosts (and passengers and guests). They verify their identity through government-issued documents, skype calls, selfies, compare pictures to documents, get access to government databases, credit records, etc. Can a fully distributed service do that? No. You’d need a centralized provider to do it. And how would the blockchain make any difference then? Well, I may not be entirely correct here. I’ve actually been thinking quite a lot about decentralized identity, e.g. a way to predictably generate a private key based on, say, biometrics+password+government-issued-documents, and use the corresponding public key as your identifier, which is then fed into reputation schemes and ultimately real-world services. But we’re not there yet.

And that is part of my fifth concern – the technology itself. We are not there yet. There are bugs, there are thefts and leaks. There are hard-forks. There isn’t sufficient understanding of the technology (I confess I don’t fully grasp all the implementation details, and they are always the key). Often the technology is advertised as “just working,” but it isn’t. The other day I read an article (lost the link) that clarifies a common misconception about smart contracts – they cannot interact with the outside world – they can’t call APIs (e.g. stock market prices, bank APIs), they can’t push or fetch data from anywhere but the blockchain. This mandates the need, again, for a centralized service that pushes the relevant information before smart contracts can pick it up. I’m pretty sure that all cool-sounding applications are not possible without extensive research. And even if/when they are, writing distributed code is hard. Debugging a smart contract is hard. Yes, hard is cool, but that doesn’t drive economic value.

I have mostly been referring to public blockchains so far. Private blockchains may have their practical application, but there’s one catch – they are not the cool distributed technology that the Bitcoin uses. They may be called “blockchains” because they…chain blocks, but they usually centralize trust. For example the Hyperledger project uses PKI, with all its benefits and risks. In these cases, a centralized authority issues the identity “tokens,” and then nodes communicate and form a shared ledger. That’s an easier problem to solve, and the nodes would usually be on actual servers in real datacenters, and not on your uncle’s Windows XP. That said, hash chaining has been around for quite a long time. I did research on the matter because of a side-project of mine and it seems providing a tamper-proof/tamper-evident log/database on semi-trusted machines has been discussed in many computer science papers since the '90s. That alone is not “the magic blockchain” that will solve all of our problems, no matter what gossip protocols you sprinkle ontop.

I know I sound like a naysayer here, but I hope I’ve pointed out particular issues, rather than aimlessly ranting at the hype (though that’s tempting as well). I’m confident that blockchain-like technologies will have their practical applications, and we will see some successful, widely-adopted services and solutions based on that. But I’m not convinced it will be revolutionizing.

I hope I’m proven wrong, though, because watching a revolutionizing technology closely and even being part of it would be quite cool.

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Topics:
blockchain ,security ,distributed systems

Published at DZone with permission of Bozhidar Bozhanov, DZone MVB. See the original article here.

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