What Is a Block?
Blocks within a blockchain are arranged sequentially, with new blocks added at the end of the chain.
Each block contains a reference to the previous block in the form of a hash, a crucial security feature of blockchain technology, making it highly resistant to tampering or forgery.
Block Structure
In addition to a timestamp and a record of transactions, each block also includes the solution to a unique cryptographic puzzle.
This puzzle must be solved through mining for a new block to be added to the blockchain.
Miners who successfully solve the puzzle are rewarded, and thus, the details of the rewarded addresses are included as the first transaction in each block.
In the case of the Bitcoin blockchain, the difficulty of the cryptographic puzzle is automatically adjusted by the network every 2,016 blocks to maintain a targeted solution rate.
Genesis Block and Blockchain Security
The first block in a blockchain is known as the genesis block, and it does not reference any previous block since it is the starting point of the chain.
The block structure of a blockchain ensures its high level of security and integrity.
Each block in the chain contains a hashed reference to all the preceding data, making it extremely challenging to alter any record within the blockchain.
To modify a single record, a malicious actor must change every block in the chain, which is practically impossible.
Moreover, the decentralized nature of blockchains ensures that the blockchain is stored on the local computers of all its users, further safeguarding against hacking or falsification attempts.