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10. Verification Rules

Every card read must re-verify the entire card state from scratch. No cached assumption about a previously valid read may be carried forward.

Tamper conditions​

A card is treated as tampered if any of the following fail:

  • Cryptographic integrity — the authentication tag or HMAC over the payload does not match
  • Log chain integrity — any entry in the transaction log chain is inconsistent with its predecessor
  • State consistency — the balance, counter, or timestamp recorded in the wallet block is inconsistent with the log history
  • Counter or timestamp rollback — the monotonic counter or last-write timestamp has moved backwards, indicating a replay or rollback attack

Additional checks​

  • The session window must still be valid at read time.
  • State transitions must conform to the card state machine; invalid transitions are treated as suspicious.
  • Any field or flag combination that is undefined or contradictory is rejected.

Response to a failed verification​

  • Do not write to the card.
  • Escalate the card status to blocked if writable; report to the backend if not.
  • Display a generic blocked message; do not expose cryptographic details.

Exact ordered validation sequence with field-level checks: Tech Specs §5 Tamper Detection & Validation.