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Hash chain.

also: hash chains · hash chaining · tamper-evident · tamper evidence · tamper-evidence

Each log entry stores a hash covering the previous entry's hash, so changing any past entry breaks every hash after it.

the two-minute refresher

Each event stores previous_hash and its own event_hash, computed over the event including previous_hash.
Verification recomputes the chain; a mismatch pinpoints tampering.
Tamper-evident, not tamper-proof, and only if the latest hash is checkpointed where attackers can't rewrite it.
Prevention comes from immutable storage (S3 Object Lock) and no UPDATE/DELETE permissions.

Where the course teaches it

W03 · Day 5Audit Log Systemlearn it →W03 · Day 5Audit Log Systemrevisit →

Related concepts

Audit log