Aadhaar Detection: Verhoeff Checksums and Why Regex Isn't Enough

Pattern matching is only the first gate

The naive approach to Aadhaar detection is a regex: twelve consecutive digits. This pattern matches Aadhaar numbers, but it also matches invoice numbers, timestamps, and random test data.

Adding Verhoeff validation reduced false positives by over 90% compared to regex-only detection.

PAN, UPI, and other Indian identifiers

PAN cards follow a strict format: five uppercase letters, four digits, one uppercase letter. UPI IDs follow the format user@provider. Indian mobile numbers are 10 digits starting with 6-9.

Each identifier has its own validation rules beyond simple pattern matching. CrewCheck implements specific validators for each type.

Detection as an evidence problem

PII detection is not just about blocking sensitive data. It is about creating evidence that you attempted to detect and redact personal data.

Every PII detection event in CrewCheck is logged in the trust ledger with the type, confidence level, action taken, and the original and redacted text.

How to operationalize this

Treat this topic as a production workflow, not a policy note. Identify the user action that starts the AI call, the personal or regulated data that can enter the prompt, the model provider that receives it, and the owner responsible for changing the route when something goes wrong. That simple inventory is often where weak AI governance becomes visible.

Once the workflow is named, put the control at the boundary. For CrewCheck, that means routing the model call through the gateway so detection, redaction, rule evaluation, provider choice, and audit logging happen consistently. The important detail is that the control should run on every request, including retries, fallback providers, demos, and internal admin tools.

What evidence a buyer should ask for

A serious buyer should ask for evidence that connects the claim to live behavior. For a privacy claim, that means redaction logs, blocked examples, sanitized payloads, and data-retention behavior. For a safety claim, that means red-team cases, circuit-breaker decisions, and output scanning results. For a compliance claim, that means the notice, purpose, rule, and provider route can be reconstructed from the audit trail.

The practical standard is whether the team can answer a specific question without manual archaeology: what happened to this request, which rule fired, what data was removed, which provider saw the final payload, and who can approve or reverse the decision? If that answer requires five tools and a memory of how the system was meant to work, the evidence layer is not ready yet.

A safe next step

Start with one high-risk path and make it boringly inspectable. Run realistic Indian examples through it, including Aadhaar-like numbers, PAN formats, UPI IDs, mixed-language prompts, and attempts to override system instructions. Check the user-facing response, the gateway event, the dashboard state, and the exportable report. The path is ready only when all four tell the same story.

That narrow verification habit matters more than a large compliance checklist. AI governance fails when teams assume controls are present because the architecture says they are. It becomes trustworthy when the live product can show the exact request, exact decision, and exact evidence behind the claim.

After that, make the check repeatable. Keep the examples in a small regression pack, rerun them before deployment, and compare the result with the public claim you are about to make. If the route, report, or dashboard no longer proves the claim, change the product or change the claim before a customer finds the gap.

The habit is deliberately plain: one workflow, one owner, one evidence trail, one live verification path. That is enough to turn a short article or launch note into something an operator can actually use.