The concept of blockchain emerged about ten years ago in a white paper by Satoshi Nakamoto who developed the bitcoin. Part of this process was to devise the blockchain technology. It is commonly described as “an open, distributed ledger that can record transactions between two parties efficiently and in a verifiable and permanent way”.
The blockchain can be seen as a large distributed database in which each node has a copy of it. With each transaction, the state of the blockchain, also known as the “world state”, changes from a consistent one to another. Each of these transactions is validated using cryptographic tools by a subset of the total nodes (i.e. the miners). This transaction is then added to the previous ones to form a block that will be chained to the preceding one; thus the blockchain. The transactions and the blocks are put together using the hash value of the previous element. That means, that changing one transaction requires to change all the ones following. Altering data would need an almost impossible computation to stay consistent in regards of the whole because all the resulting hash value would have to be computed back. This feature is responsible in making the blockchain immutable.
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