What is Blockchain?
This article defines the fundamental of blockchain and why it is immutable.
I’m a Software Engineer at Simpel from Canberra, Australia. Blockchain enthusiast working on own project, happy to learn and teach about blockchain and web 3.0 projects.
The blockchain data structure is a back-linked, ordered list of transaction blocks. The blockchain can be saved as a simple database or as a flat file. The blockchain metadata is stores by the Bitcoin Core client using Google's LevelDB database. Each block in the chain is linked "back," with each referencing to the one before it. The blockchain is always seen as a vertical stack, with blocks stacked on top of one another and the first block serving as the stack's foundation also known as genesis block.
Each block in the blockchain is defined by a hash produced on the block's header using the SHA256 cryptographic hash algorithm.The "previous block hash" field in the block header also refers to a previous block, referred to as the parent block. In other words, each block's header contains the hash of its parent. The chain of hashes connecting each block to its parent extends all the way back to the genesis block, the first block ever created.
Even though a block has only one parent, it can have several children at any given time. Each children refers to same genesis block, and the "previous block hash" field includes the same (parent) hash.
During a blockchain "fork," which occurs when distinct blocks are discovered almost simultaneously by different miners, several children emerge.
The "fork" is eventually resolved when only one child block remains in the blockchain.
Despite the fact that a block might have multiple children, each block can only have one parent. This is due to the fact that each block has only one "previous block hash" field that refers to its single parent.
The "previous block hash" field is located within the block header and hence impacts the hash of the current block. When a parent's identity changes, the child's identity changes as well. The parent's hash changes if the parent is changed in any way. The child's "previous block hash" pointer must be updated as a result of the parent's modified hash. This changes the hash of the child, which requires a change in the grandchild's pointer, which changes the grandchild, and so on. This cascade effect guarantees that if a block has several generations after it, it cannot be modified without causing all subsequent blocks to be recalculated. The existence of a long chain of blocks makes the blockchain's deep history immutable, which is a key feature of bitcoin's security. Because such a recalculation would require absolutely huge computation (and thus energy consumption), the existence of a long chain of blocks makes the blockchain's deep history immutable.
Blockchain is growing and blockchain technology is highly in demand. If you are interested in blockchain I suggest please go through the Bitcoin white paper by Satoshi Nakamoto .
Reference: https://github.com/bitcoinbook
Blockchain | Chapter 01
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