what is the blockchain?

A system in which a record of transactions made in bitcoin or another cryptocurrency are maintained across several computers that are linked in a peer-to-peer network.

Source: Oxford Dictionary

Blockchain is a revolutionary new type of database

First of all, there is not a single blockchain – there are many! When talking about “the” blockchain, the first and “oldest” one is usually referenced: the blockchain that drives bitcoin, the first modern cryptocurrency.

But what IS it? The definition in the Oxford dictionary doesn’t tell us a lot, that is for sure 🙂

A blockchain is a distributed ledger of transactions. In some ways, it behaves much like a database – but unlike every other database, its entries build on top of each other. Whenever a transaction is written in the blockchain, as part of a so called block, it is linked to the proceeding entries in the blockchain and secured using cryptography. This enables a high degree of security: tampering with even one transaction within the blockchain does immediately de-validate the whole chain of cryptographic proof within the blockchain. Hence the “chain”: Every block references the one before it – going back to the first block written to the blockchain.

But what about the “distributed” part? A blockchain (only talking about public blockchains here, go here to find out about other types of blockchains ) does not live on a central server. It lives on multiple “nodes”, each storing a complete copy of the blockchain. The security of the blockchain – and certainty that its entries are correct – does not come from the trust one has in a node. More specifically: the blockchain is built so that you do not have to trust any node! As the state of each node is transparent (the blockchain can be read and examined from outside easily), only those nodes where the state of the blockchain is completely identical to the majority of all other nodes are being accepted as being correct. Big blockchains, like the bitcoin one, run on thousands of nodes – bitcoin has over 11.000 nodes at the time this article is written (October 2017). This makes it economically unviable and technically very very difficult to maliciously alter the accepted true state of the blockchain – to hack it. Massive amounts of computing resources would be necessary – so much so, that the money spent for hacking the blockchain exceeds greatly the amount of money to be gained from hacking it.

Good starting points for learning more about the inner workings of a blockchain are the following resources:

what makes airproof so secure?

airproof uses the cryptographic security of the blockchain to provide highly secure, but very cost effective “proof of existence” for your airproof video

Airproof utilizes the core strengths and functionality of blockchain technology to secure your stay.

  • Hashing
    When talking about the digital fingerprint that airproof makes of your airproof video, what we really talk about is a hash. If you are so inclined, you can read up on the SHA standard on its wikipedia page here. In simple words, a hash is a string of hexadecimal values which is calculated from a digital file. The method by which it is calculated only works one way – you can calculate the hash from the original file, but you cannot recreate the original file from the hash. Also, as the original file gets bigger in size, the hash always has the same size (256 bits in length for the method we use, called SHA-256). Even small changes in the original file result in a different hash value, making it easy to check if a digital file has been altered.
  • Timestamping
    Every transaction that is written in a block is getting timestamped. Where there was a real stamp in the old days, now it is an exact time and date written into the cryptographic proof of the block. If someone should try to alter the time stamp of the block, he de-validates the block itself – so “changing the time” is just as impossible in a blockchain as changing a transaction itself.
  • No central source of trust
    In contrast to other solutions, there is no central authority that one must trust. We at chain.ventures, the makers of airproof, are not excluding ourselves! Whilst our app offers you a lot of convenience, as we deal with all the technology for you, the app itself is not part of the “chain of trust” between the video you have taken and the cryptographic proof of existence that is stored in the blockchain. This is why in the app, you can click on “send airproof email” and send yourself a detailed description of how you can validate your airproof video’s state and its timestamp without the airproof app itself.
  • Low transaction costs
    On a blockchain, transaction costs can be very low compared to other systems, as all validation and security checks are completely automated and the blockchain itself can run on public internet servers without any special security requirements as to the hardware, the connection, etc…. there also is no central authority with staff, overhead etc. whose costs must be factored into a transaction.

Currently, airproof stores the timestamp of your airproof video in the bitcoin blockchain via a service called opentimestamps. Opentimestamps aggregates many hashes from various applications in a so called merkle tree and timestamps this aggregate in the bitcoin blockchain. This enables us to provide airproof free of charge in version 1. In the future, to provide even more accurate timestamping and other added services, we consider also offering direct timestamping in the blockchain, and might also use the blockchain of other established cryptocurrencies. Read more about this on our roadmap!