What Port 3496 Is
Port 3496 is a registered port assigned to seclayer-tls — "security layer over TLS" — by IANA in March 2002. The registrant was Arno Hollosi, one of the architects of the Austrian Citizen Card (Bürgerkarte) system.
It's not unassigned. It's narrowly assigned to a piece of national digital identity infrastructure most people outside Austria have never heard of.
The Austrian Citizen Card
In 2000, the Austrian government resolved to build something genuinely ambitious: a digital identity system for citizens, built on smart cards, that would let people sign documents, authenticate with government services, and conduct legally binding transactions online.
The result was the Bürgerkarte — the Citizen Card. It wasn't one physical card, but a concept: any chip card (including health insurance cards) loaded with the right certificate could serve as your legal digital identity.
The infrastructure that made this work was called the Security Layer — a standardized interface between web applications and the smart card environment on your local machine. An application submits a signing request to the Security Layer. The Security Layer communicates with your card reader. You interact with the UI. A signed response comes back.
Port 3496 was where that conversation started.
How It Worked
The Security Layer ran as a local server on your computer — software that bridged the web and your physical card. The default HTTPS binding was 127.0.0.1:3496.
When you clicked "Sign with Citizen Card" on a government website, your browser sent a request to https://localhost:3496. The local software received it, prompted you to confirm, sent the data to your card reader, and returned the cryptographic signature. The website never touched your card directly — the Security Layer enforced that boundary.
It was, in 2002, a remarkably sophisticated design: TLS-secured, locally sandboxed, with a standardized XML-based protocol. Austria was building digital signature infrastructure that much of Europe wouldn't attempt for another decade.
The Range
Port 3496 falls in the registered ports range (1024–49151). These ports are assigned by IANA for specific services, though assignment doesn't guarantee widespread use. Unlike the well-known ports (0–1023), registered ports don't require elevated privileges to bind on most systems.
IANA assigns TCP and UDP for port 3496, though only TCP was used in practice for the HTTPS binding.
If You See This Port
On a modern machine, you're unlikely to encounter port 3496 in the wild. The Austrian Citizen Card system has been superseded by newer identity solutions. The local Security Layer software is no longer commonly installed.
If you see something listening on port 3496:
On a modern system, activity on this port is unexpected and worth investigating.
Why Registered Ports Matter
The registered port range is the middle ground of the port system. Well-known ports (0–1023) are reserved for foundational protocols: HTTP at 80, HTTPS at 443, SSH at 22. Ephemeral ports (49152–65535) are handed out temporarily for outgoing connections. Registered ports sit between them — claimed for specific purposes, used when those purposes are active.
Port 3496 is a small example of how this range works in practice: a government initiative needed a stable, predictable port for local software, registered it, and built infrastructure around it. The port outlasted the software. The registration remains.
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