Blockchain consists of a single record which consensus is distributed among the different nodes of a network.

What does this mean?

The blockchain is a kind of database, where information is stored in the aforementioned "blocks" in such a way that an unalterable record is created. Blockchain technology can store different types of data: in the case of Bitcoin, for example, it merely records the transactions that users make to each other, as if it were a ledger.

The registry is public: the data stored there is accessible to everyone. Each node in the network stores a complete copy of the blockchain. That means that Blockchain is not hosted in one place, but in each member of the network. Thus, the information is available at all times, with no risk of a single server going down or being attacked.

This decentralization adds an extra layer of security: an attacker can target one node in the network, but cannot attack all of them at the same time.

What does consensus imply?

Each time a block with transactions is formed, the nodes that make up the network verify its validity. They are the ones who decide on the correct blockchain. The valid chain is the one that gathers the consensus of its members.

Maliciously altering the blockchain is computationally very complex. For a change to be considered valid by the nodes, more than 50% of them should contain the false information. The entire chain would have to be modified at each of the nodes for it to be taken as the correct chain. The more nodes that make up the network, the more difficult it will be for an individual attacker to alter the consensus achieved on the blockchain.

Why can't a block be altered?

The unalterability of a block grows as new blocks are added to the chain: each one is linked through cryptographic technology to the previous one. If the information stored in the block were to be modified, its linkage with the previous block would be damaged, so that the nodes in charge of verifying the block's validity would quickly consider it invalid.

Thus, the content of the blocks, and therefore of the chain, is immutable, and its authenticity can be assured, a feature that grows as the chain is extended.

Blockchain allows us to store information that cannot be modified, lost or deleted. Just as Bitcoin was the first application of this type of technology to a digital currency, the use cases are growing all the time. The concept of an immutable and decentralized database whose integrity is guaranteed by cryptographic technology is attractive for certifying and validating any type of information.

Ethereum has been moving in this direction since its creation. It is a programmable blockchain, so far the one with the largest number of decentralized applications (DApps) built on its network for different purposes.

The fields of application of blockchain technology are growing. It is an innovation that will reshape many of the systems that today operate in a centralized manner and do not benefit from its transparency, security and immutability.

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