Block Chain - Chain – Sequence of Blocks Linked Together Cryptographically

1. Definition

In blockchain, the “chain” refers to a continuous sequence of blocks (containers of data/transactions) that are securely connected using cryptographic hashes.

• Each new block contains a reference (hash) to the previous block.

• This linking creates a chain-like structure → hence the name blockchain.

2. How It Works

• Hash Function: Every block is given a unique digital fingerprint (hash) based on its data.

• Linking: Each block stores the hash of the previous block.

• Tamper Resistance: If anyone tries to change a block’s data, its hash changes → which breaks the chain → making tampering immediately detectable.

3. Structure Example

• Block 1 (Genesis Block): The first block, with no previous block reference.

• Block 2: Contains its own data + the hash of Block 1.

• Block 3: Contains its own data + the hash of Block 2.

• And so on...

This creates an unbroken chain of trust back to the very first block.

4. Benefits of Cryptographic Linking

• Immutability: Data, once added, cannot be changed without altering all subsequent blocks.

• Security: Makes it nearly impossible for attackers to rewrite history.

• Transparency: The full chain of transactions is visible to all participants.

5. Example

• In Bitcoin, every block contains:

  • Transaction data

  • A timestamp

  • Its own hash

  • The previous block’s hash

• This ensures that if someone tries to modify Block #100, all later blocks (#101, #102, …) become invalid unless recalculated — which is computationally impractical.

 In short:
The chain in blockchain is a securely linked series of blocks, where each block references the previous one using cryptographic hashes. This design guarantees integrity, immutability, and trust in the system.