When a document is missing on the job site, it costs time and money.

Lindner Group — inGo, digital construction site compliance.

A worker arrives at the job site in the morning, holds their smartphone up to the barrier, and passes through in seconds. No security guard, no binder, no line. What looks so routine was unthinkable on the same project just a short time before: more than 1,000 paper documents, five to ten minutes of waiting time per person, every morning, for every worker. The difference between these two moments is the result of a project with the Lindner Group.

The general contractor is liable. Including for what the subcontractor forgot.

For the Lindner Group, Germany's largest privately owned construction company with more than 7,500 employees and projects in over 40 countries, this was not an abstract risk. On large construction sites, people from dozens of companies work side by side. Every one of them must present certain documents: ID, work permit, qualification certificates, proof of insurance. Anyone without a document does not get in. In the worst case: construction stops.

In Germany, customs authorities opened more than 97,000 investigations into illegal employment in 2024. Total damages exceeded 766 million euros. General contractors are liable not only for their own workforce but also for the subcontractors they hire. Fines of up to 500,000 euros, construction stoppages, and exclusion from public tenders are the consequences.

This is where a credential becomes site access.

This is exactly where inGo comes in. inGo is a digital compliance platform for subcontractor management on construction sites, developed according to SSI principles (Self-Sovereign Identity) and built on the SOWL suite by esatus. The system consists of a management suite for the organizational side and a mobile app for workers.

The general contractor defines in the system which credentials are required for a project. Subcontractors upload their employees' documents in advance. The platform checks completeness and validity. Once all requirements are met, the app generates a personal QR code that serves as a digital site access pass.

Via open interfaces, inGo is directly connected to turnstiles and physical access systems. On a security-relevant construction site in Berlin, this functionality is already in daily operation: workers scan their QR code, authorization is verified in real time, and access is automatically granted or denied.

Verify once. Use it on the next project right away.

Credentials do not need to be collected from scratch for each project. Qualifications verified once are available for future projects. Subcontractors build up a reusable digital profile. Workers have all required documents organized in the app.

All verification processes are fully logged. During a customs inspection, for example, all credentials are immediately available digitally. Audit preparation that used to take days now takes minutes.

Before inGo: more than 1,000 paper documents per project, five to ten minutes of verification time per person, error rate of up to 15 percent. With inGo: fewer than 300 digital credentials, under five seconds of verification time, error rate below one percent.

All credentials remain on the workers' devices. Documents that the general contractor receives for review are automatically deleted from their environment after approval. Data is processed in compliance with GDPR.

Wherever external workers need credentials and paper is not enough.

inGo is fully aligned with the EUDI Wallet under eIDAS 2.0. Workers from EU member states will be able to prove their identity directly via the EUDI Wallet in the future, without copies, without paper documents. The architecture is modular.

What was developed for construction sites applies wherever external workers or subcontractors are subject to documentation requirements and compliance has so far been ensured through manual processes: logistics, energy, facility management, events. The pattern is the same. So is the liability.