What is the CSI?
Definition
The proof and audit subsystem within the CSL that makes impressions verifiable, tamper-evident, and reproducibly billable.
Design principles
- Append-only: Sponsoring events are recorded immutably. Corrections are added as new events rather than rewriting history.
- Tamper-evident: Manipulation of the event history becomes detectable.
- Deterministic: The same events processed under the same rules always produce the same billing result.
- Verifiable: Advertisers receive signed evidence packages, called Proof Packs, that allow independent invoice verification.
Why this matters for verification
In classic ad stacks, the delivery system often reports its own numbers. CSI is designed around verifiable evidence instead of self-reporting.
For proof integrity and benchmark evidence, see Engineering Evidence.
Related
Last updated: 2026-04-20