What is Blockchain?
Blockchain is a distributed database where records (transactions) are grouped into blocks that are cryptographically linked to each other, forming an immutable chain of data.
Blockchain is a distributed data storage technology where information is organized as a sequence of blocks, each containing the hash of the previous block. This creates an immutable chain of records that cannot be forged without changing all subsequent blocks.
Each block contains: (1) transaction data, (2) hash of the previous block, (3) timestamp, (4) nonce for proof-of-work. Through decentralization, copies of the blockchain are stored on thousands of nodes, making the system resistant to censorship and failures.
Key properties: immutability, transparency, decentralization, consensus. Blockchain underpins Bitcoin, Ethereum, and other cryptocurrencies, but is also used for supply chain, digital identities, and smart contracts.
🧒 Explain Like I'm 5
Imagine a notebook where each page is glued to the previous one with special glue. If someone tries to change a record on one page, the whole notebook falls apart. Now imagine thousands of people have the same notebook simultaneously—that's blockchain!
❓ Frequently Asked Questions
How does blockchain differ from a regular database?
The main difference is decentralization and immutability. In a regular database, an administrator can change any record. In blockchain, changes require consensus from the majority of nodes, and the history of changes is preserved forever.
Can data be deleted from blockchain?
No, this is a fundamental property of the technology. All records in blockchain are immutable. You can add a new record to cancel a previous transaction, but the historical record remains forever.
Is blockchain always public?
No. There are public (Bitcoin, Ethereum) and private (Hyperledger, Corda) blockchain networks. In private blockchains, read/write access is limited to a specific group of participants.
What is the difference between public and private blockchain?
Public blockchains (Bitcoin, Ethereum) are open to anyone, fully decentralized, and transparent. Private blockchains restrict access to approved participants, offer faster transactions, and are used by enterprises for internal processes while maintaining some blockchain benefits like immutability.
Can blockchain be hacked?
While blockchain itself is extremely secure due to cryptography and distribution, vulnerabilities exist: 51% attacks (if one entity controls majority of mining power), smart contract bugs, and exchange hacks. Major public blockchains like Bitcoin have never been successfully hacked at the protocol level.
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