Hero Sample — TamperProof

Concept: Hash-chained event streams catch direct-DB tampering at the next verification pass. The full why lives in the Tamper-Evident Streams concept page; this is the runnable proof.

• Code: samples/Stratara.Sample.TamperProof
• Lines: ~100
• Read time: 5–10 min
• Dependencies: none — pure in-memory, no database, no DI container.

What you'll see

1. HashChainedEventStore — every Append computes SHA-256(previousHash || canonical-json(payload)) and stores both the entry's own hash and a pointer to the previous entry's hash.
2. Three events appended — AccountOpened, AmountDeposited, AmountWithdrawn. The console prints each entry with a six-byte hash preview so the chain is visually inspectable.
3. ChainVerifier.Verify — the clean run passes. Every stored hash matches a fresh re-hash; every previous-hash pointer matches the prior entry's hash.
4. TamperWithPayloadForDemo — simulates an attacker editing entry #2 directly in the database, rewriting $50 to $5000. The stored hash is untouched.
5. ChainVerifier.Verify again — raises EventStreamCorruptedException at sequence #2 with a precise reason: "stored hash does not match a fresh re-hash of the payload (payload was modified after commit)".

Running

dotnet run --project samples/Stratara.Sample.TamperProof

Expected output (abridged):

=== Stratara TamperProof ===

--- Append three events ---
  #1  AccountOpened         hash=70be4f…
  #2  AmountDeposited       hash=796018…
  #3  AmountWithdrawn       hash=6a0260…

--- Verify the chain (clean) ---
  OK — every entry's stored hash matches a fresh re-hash of its payload.
  OK — every entry's previous-hash pointer matches the prior entry's hash.

--- Tamper: rewrite entry #2's deposit from $50 to $5000 ---

--- Verify the chain (tampered) ---
  CAUGHT: Event stream tampering detected at sequence #2: stored hash does not match a fresh re-hash of the payload (payload was modified after commit)

How this maps to the real Stratara

Sample	Real Stratara
HashChainedEventStore (in-memory list)	Hash columns on event_stream_entry populated by EF Core
ChainVerifier.Verify (on-demand)	EventStreamHashingWorker from the Stratara.EventSourcing.WorkerDefaults composite — runs as a background service, processes batches, surfaces breaks via OpenTelemetry counters + structured logs
TamperWithPayloadForDemo	No equivalent — production code has no public mutation path on persisted entries

Sister hero sample

• Hero Sample — Encryption — the confidentiality counterpart. Same goal of integrity-by-construction, applied at the field level instead of the stream level.