How would we remember Bitcoin?No, it is not a start of an obituary, and no one buries anyone!What I am asking is, what the specialness of Bitcoin technology is, what novelties it has?We have seen e-cash before it (DigiCash by David Chaum), , and digital signatures can actually be considered as classics.Not a novelty, yet a warmer guess.Some might say that a combination of abovementioned is the winning hand, but I would like to emphasize a single feature.Had the first blockchain-based application been not Bitcoin and its coins, but a BitZombie (a service for coordinating survivors in case of a Zombie-apocalypse), then it would be called the innovation that changed the world.Blockchain is not a simple decentralized database, which is completely stored by each network node.Its unique feature lies in the fact that every user can check on his own that his copy is similar to those stored by the majority of other nodes.Absolutely similar, down to the last bit, in the same order.(naturally, there is also a margin for error, but it is negligible or it can be made as small as one would wish).

The key point is "on his own", meaning that one should not trust other nodes to sustain the network (trusting mathematics is better).In practice, it is a solution to the problem known as "Byzantine Fault Tolerance".Scientists call it the .Naturally, storing complete blockchain at one's computer is not mandatory.The data inside the blocks is stored as a tree, so it is possible to ensure that a "leaf" of the tree (transaction or any other data) is included in the chain without downloading its full version.If at least one node exists in the network, we can say that the blockchain exists as well.Practically, it is like a perpetuum mobile that cannot be stopped by anyone and anything (short of the Big Freeze).It is the blockchain technology that makes Bitcoin so wonderful.Still, it causes a question: is the technology applicable anywhere besides finances and zombie apocalypse?And yet another one: can we justify such application?Today, we are going to try to find this out by evaluating different services based on blockchain.

We shall start with the first alternative application of blockchain, in the historical order: the project of distributed DNS, .Its goal is to allow registering standard DNS records, performing standard operations (e.g.update) on them and, naturally, gaining access to them.This way, any client in possession of a copy of actual blockchain can easily check, which IP at a certain moment of time corresponds with a particular website address.The benefit lies in decentralization; one cannot censor or block all nodes in the network simultaneously.It is quite simple to imagine a basic principle of operation for Namecoin.Let a transaction contain some additional data, which is not related to the coins themselves. -- -- " and pay additional fee for such transaction. -- -- ", again at a certain price.Naturally, in addition to the fee size, other rules are required.For instance, a transaction "REGISTER name" is considered invalid if a "name" record already exists in the blockchain and is active (Namecoin records should be updated every 36000 blocks, i.e.

Moreover, the record update must be signed with the same key used for creating it in the first place to prove the ownership right.Namecoin, however, does not protect against cybersquatting.As no centralized register is present, there is no way to file a complaint in case someone else has occupied your trademark.litecoin communityObviously, such 'business' requires funds, just like cybersquatting outside of blockchain.bitcoin miner live cdBut what if a squatter sees your registering transaction and instantly sends his own with the same data?world's fastest bitcoin minerIt is clear that only one of them will be included into blockchain; therefore, he will be able to intercept your domain with 50% probability.litecoin block data

To deal with such threat, Namecoin includes the following ingenious mechanism: the first transaction is a record "REGISTER HASH ", where hash is the hash of your registration request.Said hash does not give any clue to the domain name, so a squatter would not be able to capture it even by sending another hash-application.litecoin hash rate vs difficultyIt is useless for him.bitcoin worth 100 000An honest owner, however, will send a second transaction with complete data later.darknet bitcoinThe system checks that the hash of this transaction is already in the blockchain and accepts registration.bitcoin lovers unitedGenerally, Namecoin can be regarded as a convenient tool (being first of its kind at the very least), which fulfills its task.bitcoin xrp

A non-libertarian might not like the absence of a cassational instance, but even she should appreciate the fact that decentralization protects against many serious problems: censorship, DDoS etc. Blockchain is a database.Anything can be stored within it (theoretically), up to .Then, let us store whatever we want there!This is the way one can describe the approach of the .This altcoin features a simple possibility to attach files up to 128 kb to the transaction, naturally, at a fee.The file can be accessed at any time due to 'indestructible' p2p network.Still, I would not call this scheme convenient.The file is bound to stay in the blockchain forever.It only benefits its owner, while other users have to do the job of transferring and storing it.We can say that the fee for the data is uniformly 'spread out' between all miners, but not all the nodes are miners!Moreover, you cannot delete the file from the blockchain (even if it is obsolete or you want to get rid of it).approach is of a more serious kind.

We are not going into details now; general idea will suffice.The main difference from Datacoin lies in the fact that a user is rewarded even for storing a part of the blockchain on his computer, i.e.he practically becomes a miner.The one who allocates 20 GB gets twice as much as the one with 10 GB.The coins acquired in the course of such mining can be spent on placing your own data in the blockchain.The practical side of this approach is described and .StorJ seems to be a kind of Bittorent Sync, without the altruism.It means that the scheme is not based on the kindness, but on regular market relations.The latter, of course, is often the best basis.Bruce Schneier gives the following protocol as an example in his book Applied Cryptography: Can you see the problem here?We have to trust Trent and expect him to put a correct date, not to mess with the signature and be cooperative.However, no person is indispensable, so blockchain comes out again as an impartial and honest intermediary.The implements a simple function.

It puts the hash of any file in the transaction that gets into Bitcoin's blockchain.Actually, such operation is so simple one could do it manually.What is the catch?In his original whitepaper, Satoshi Nakamoto calls blockchain a "distributed timestamp server".This is not an accident.Blockchain not only protects the data from being changed, deleted etc., but arranges them as well.The blocks are created one by one while the order of transactions within the block is quite set, too.The block headers contain timestamps, though these are not exactly accurate (+/- hour error is allowed).This sometimes results in the first of two consequent blocks having a later timestamp then the second.It is ideal to identify (with one-hour accuracy) the moment the data appeared.Putting cryptographic hash instead of a file into the blockchain solves two problems.First, it saves storage space, as hash from any data always has fixed length (and our task does not require storing the file itself in the blockchain).

Second, hash does not disclose the file itself until the time comes, a very important feature if we consider patents, for example.There might be other services implementing this idea too.Anyway, blockchain fits ideally here; Bruce Shneier would be happy.I guess the title makes it all clear.Both projects, and , use the decentralization and invincibility of blockchain as communication platforms.Bitmessage is a considerably old project, which dates back to 2012.It uses blockchain as the message-storage.Not for all messages, of course, but only for the latest two days.Due to the tree-like structure, everything except the root hash can be deleted without compromising the integrity of the chain.Why use blockchain here?Bitmessage was not started from the scratch; it was a fork of Bitcoin, thus inheriting all structures and specifications.Transactions were converted into messages, addresses into user IDs and chat rooms.Many things have been changed since the first version, but many atavisms remain yet.

I will not go into details over the functionality: it is not directly related to the blockchain technology.What I would like to note, though, is that another Bitcoin element was used in the design as well: Proof of Work.In order to prevent spam, a simple work on finding hash must be done when sending a message.It is, essentially, a pure realization of Adam Back's Hashcash idea.Twister, as is easily seen, is an analog of Twitter.It is very similar to Bitmessage, but does not have blockchain.To be more correct, blockchain is present, but not used to store messages.Usernames are included into Bitcoin chain using almost the same registration mechanism as Namecoin has.Here we only need to establish precise correspondence 'name'-'key' (who was the first to register), so Twister's creators quite reasonably decided that separate blockchain is not required.And why would the messages need blockchain?They are not transactions, and there is no such notion as 'discrepant set of messages', when it would be important for us to know the version supported by the majority of the nodes.