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use-of-bsn.md

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title Retrieving Cases for a Particular BSN
description Best practices for securely retrieving cases by BSN, avoiding URL-based exposure of sensitive personal data.
keywords
BSN
cases
ZRC
privacy
security
POST
zoek
GDPR
AVG
OneGround
slug /cases/use-of-bsn

Retrieving Cases for a Particular BSN

Retrieving cases using a BSN (Dutch Social Security Number) can be done in two ways. While our case registration software supports both methods, many client applications are using the older, insecure method. This article explains the problem and the recommended solution.

The Problem: Leaking BSNs via GET Requests

The current, widely-used method for fetching cases by BSN is a GET request where the BSN is passed as a URL parameter:

https://zaken.oneground.local/api/v1/zaken?rol__betrokkeneIdentificatie__natuurlijkPersoon__inpBsn=123443210

This is a security and privacy risk.

The BSN is sensitive, personal data. Placing it in a URL has serious consequences:

  • Extensive Logging: Web servers, proxies, load balancers, and other network infrastructure log URLs by default. This means the BSN is stored in numerous log files across different systems.
  • Increased Exposure: These logs are often retained for long periods and accessed for monitoring, debugging, or analytics, exposing the BSN to a wider audience than necessary.
  • Privacy Violation: Unnecessarily logging sensitive data violates fundamental privacy principles (like GDPR/AVG) and creates a data leak that is difficult to contain or audit.

The Solution: Use POST /_zoek

A safer and more robust alternative is to use the POST /_zoek endpoint from the VNG Zaken API. This method allows you to send the search parameters in the request body instead of the URL.

Since request bodies are generally not logged by servers and proxies, the BSN remains secure and is not exposed in log files.

Here is an example of how to use the /_zoek endpoint. Many other attributes are also possible.

Request:

POST /api/v1/zaken/_zoek
Host: zaken.oneground.local
Content-Type: application/json

{
    "rol__betrokkeneIdentificatie__natuurlijkPersoon__inpBsn": "123443210",
    "expand": "rollen"
}

We strongly urge developers of client applications to update their implementation to use the POST /_zoek method to ensure the privacy and security of citizen data.