Use AI on client files in nLPD compliance. Staff at fiduciaries, law firms, and accounting practices handle personally identifiable information every day: client names, AVS numbers, IBANs, case references, addresses. The appeal of public tools like ChatGPT or Claude is obvious — drafting, summarising, rephrasing — but pasting a client letter into a public interface sends that data to cloud infrastructure outside your control.

Context: generative AI and client data

In Switzerland, the nLPD (revised Federal Act on Data Protection) requires transparency, proportionality, and accountability. Many teams are stuck: they want AI, but compliance says no.

The SME dilemma

Banning AI breeds shadow IT. Allowing plain-text ChatGPT exposes client data. Manual anonymisation does not scale on long files. A third path is needed.

  • Copy-paste into ChatGPT — no guarantee on where data goes or how it is reused.
  • Total AI ban — staff work around policy or lose productivity.
  • Manual anonymisation — tedious, incomplete, and unsustainable on long files.

The concept: a privacy gateway

aiproxy is a Swiss-hosted AI proxy built for law firms and fiduciaries by d-side solutions: a familiar chat interface (Claude- or ChatGPT-like) backed by a local anonymisation pipeline. Only pseudonymised text leaves Swiss infrastructure for the Claude API (Anthropic). The user then reads a reconstituted response where names and references have been automatically restored. Product site: aiproxy.ch.

Technical positioning

This is not a self-hosted LLM. It is a data protection layer between your team and a capable cloud model — with local PII detection (Microsoft Presidio), mandatory preview before sending, selective de-anonymisation, and token reconstitution in the response.

The five-step flow

aiproxy diagram: Chat, local Presidio anonymisation, prompt review, Claude, and token re-mapping — Swiss hosting
The aiproxy flow: only pseudonymised data leaves Swiss infrastructure for Claude. The token → original value mapping stays on the server.

1) Input — text or documents

The user writes a question or uploads a document (DOCX, PDF; scanned PDFs via OCR) in a web interface (browser only, zero install). Session history, Markdown rendering. Content is processed locally before anything is sent to the AI.

2) Anonymisation — Presidio locally

On each message, text is analysed on the Swiss VPS by Microsoft Presidio coupled with spaCy (large models for fr/en/de/es). Detected entities are replaced with indexed tokens. The token → original value mapping stays server-side.

Fictitious example

Before: "Mr Jean Dupont, AVS 756.1234.5678.90, case FR.2024.123, resides in Fribourg."

After: "Mr <PERSONNE_1>, AVS <AVS_1>, case <DOSSIER_1>, resides in Fribourg."

3) Prompt review — transparency before sending

The nLPD transparency panel shows the exact text that will be sent to Claude, the list of detected entities and their tokens. Preview is mandatory: the user can remove an anonymisation deemed excessive (× on an entity) before confirming the send — explicit consent before original data reaches the LLM.

4) Send — validated text only

After validation, only the pseudonymised prompt is sent to the Claude API. Conversation history stored server-side also remains anonymised. No raw documents or unmasked personal data transit to Anthropic.

5) Reconstituted response

Claude is instructed to reuse tokens verbatim in its reply. aiproxy then replaces <PERSONNE_1>, <AVS_1>, etc. with original values. The user reads a clear answer with real names — the transparency panel shows how many tokens were reconstituted.

Video demo

The video below walks through the full pipeline on a fictitious case: entering a message with personal data, Presidio anonymisation, prompt review, sending to Claude, and response re-mapping. (French audio.)

aiproxy demonstration — local anonymisation, prompt review, and re-mapped response (fictitious data).

Explore the product at aiproxy.ch — product overview, FAQ, and demo request form.

How to get started

Every project starts with a personalized demonstration. The pilot phase follows once the approach is validated with your team.

  • Step 1 — Demo (free) — 20-minute video call on a concrete use case from your practice: local anonymisation, nLPD transparency panel, and reconstituted response. No signup and no online access.
  • Step 2 — Pilot (paid) — dedicated instance on your Swiss VPS, user accounts, DOCX and PDF upload, training and onboarding support.

Request a demo on aiproxy.ch — we will contact you within 48 business hours.

Presidio and Swiss recognizers

Presidio provides entity detection (NER, patterns, context). d-side extended the engine with Swiss domain recognizers and filtering for legal false positives (e.g. art. 336 CO must not be masked as a location).

Entity Token Example
Person<PERSONNE_N>Jean Dupont
AVS number<AVS_N>756.1234.5678.90
IBAN CH<IBAN_N>CH93 0076 2011 6238 5295 7
IDE number<IDE_N>CHE-123.456.789
Case / file ref.<DOSSIER_N>FR.2024.123
Phone<TEL_CH_N>+41 26 123 45 67
Company<ENTREPRISE_N>Dupont SA
Email<EMAIL_N>client@example.ch

Multilingual detection (French, German, English, Spanish) via Lingua before Presidio analysis. Stack: FastAPI, Docker, nginx, hosted on Infomaniak VPS in Switzerland.

nLPD transparency

The principle is not to hide anonymisation — it is to make it visible and controllable:

  • ✓Transparency panel — text sent to Claude, detected language, badges per entity type.
  • ✓Review before sending — mandatory preview and selective de-anonymisation per entity.
  • ✓Data sovereignty — anonymisation, mapping, and hosting on Swiss infrastructure (Infomaniak VPS).
  • ✓Document upload — DOCX, PDF, and scanned PDFs (OCR), anonymised locally before sending.

Who it is for

aiproxy targets law firms, fiduciaries, and Swiss SMEs that handle personal data and want to offer AI to their teams without compromising client confidentiality:

  • Fiduciaries and accounting practices
  • Law firms and legal practices
  • Any organisation blocked by internal policy on public AI tools

In summary

aiproxy combines a modern AI chat experience with local Presidio anonymisation, nLPD-compliant prompt review, and automatic response reconstitution — all hosted in Switzerland.

Your team gains productivity. Your client data does not leave in plain text for the cloud.

Want to see aiproxy on a case from your practice? Request a 20-minute demo on aiproxy.ch.

LD

Luc Demierre

Founder & IT Consultant — d-side solutions Sàrl, Bulle

Specialized in IT architecture, systems security and AI integration for Swiss SMEs. Founder of d-side solutions Sàrl since 2022.

Frequently asked questions

Where is d-side solutions based?
d-side solutions is located at Chemin du Carry 7, 1630 Bulle, in the canton of Fribourg, Switzerland. These case studies are written by our local team.
Do you take on projects in Bulle and Fribourg?
Yes. We support SMEs in the canton of Fribourg, the Gruyère region, and Romandy, as well as mandates across Switzerland.
Can we use AI on client files while staying nLPD-compliant?
Yes — if you control what leaves your infrastructure. aiproxy anonymizes personal data locally (Presidio + Swiss recognizers), shows the pseudonymized prompt before sending, and only transmits validated text to Claude. Explore the product at aiproxy.ch — d-side solutions, based in Bulle (Fribourg), deploys and supports this solution for fiduciaries, law firms, and Swiss SMEs.
What document types are supported?
Users can enter free text or upload DOCX and PDF documents (including scanned PDFs via OCR). Content is anonymized locally on the Swiss server before any send to the AI.
What is the difference between the free demo and the paid pilot?
The demo is a 20-minute presentation on a concrete use case from your practice, via video call, without access to the application. The pilot is a paid phase after the demo: dedicated instance on your Swiss VPS, user accounts, document upload, and onboarding support. Request a demo at aiproxy.ch.
How do I get a demo?
Fill in the form at aiproxy.ch. We will contact you within 48 business hours to schedule a personalized 20-minute video call — no commitment and no signup required.