Let’s dissect a 80-byte Block Header:
- Version: Block version number
- Previous Block Hash: Hash of the prior block header (32 bytes)
- Merkle Root: Combined cryptographic summary of all transactions (32 bytes)
- Timestamp: Current Unix epoch timestamp
- Bits (Target): Mining difficulty target threshold
- Nonce: 4-byte arbitrary counter iterated during Proof of Work
Miners alter the Nonce (and extra nonce in coinbase) continuously until the SHA-256 hash of this 80-byte header falls below the target.
🧠 Today's Key Takeaway
- Block headers are compact 80-byte data structures containing Merkle roots and nonces.
- Miners hash the header data repeatedly to satisfy difficulty target criteria.
