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Security Fundamentals & Crypto · Intermediate

Blockchain

Distributed, append-only ledger where blocks are cryptographically chained by hashes to resist tampering.

Definition

Each block contains a hash of the previous block, so altering one block invalidates every subsequent block. Consensus mechanisms such as proof of work or proof of stake let distributed participants agree on the ledger. Security+ calls this an open public ledger and highlights its integrity properties.

Example

Bitcoin blocks each store the SHA-256 double hash of the preceding block header.

Exam tip

Blockchain provides integrity and transparency, not confidentiality.

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