How I finally got proCertum SmartSign running on Linux? (A report from a journey that took years)

I've been using Linux daily since at least 2003 — first Ubuntu, then Zorin OS, sometimes Pop!_OS, and even Gentoo at one point. I'm attached to this system like an old dog to its kennel. Unfortunately, one thing has always annoyed me: the qualified signature from Certum. At work, the standard was Windows, where proCertum SmartSign worked flawlessly. But on my Linux machine, I must have installed that application about ten times, and every single time the result was the same: the program launched, showed its interface, but did not see the USB key. As if it wasn't there. Zero reaction.

The background of the problem, or "we'll help, but not really"

Once — about two years ago — I even contacted Certum technical support. The response I got was, to say the least, disarming: the desktop environment should be something other than Gnome. Right. Except I've always used Gnome and I'm not changing my desktop just to sign one document. That response effectively discouraged me, and for a long time I made peace with the fact that I would have to fire up a Windows virtual machine just to sign something.

A moment of enlightenment and a bit of stubbornness

Only now, on the occasion of another attempt (the eleventh, I think), did I decide to approach the matter differently. I had a moment of free time and thought: "Listen, this has to work. It's just a matter of finding that one missing piece." And so, instead of immediately cursing the manufacturer, I sat down and started searching methodically.

Step 1: Does the system even see the reader?

To begin with, I plugged in the reader — small, black, from ACS (Advanced Card Systems), model ACR39U. I opened a terminal and typed:

lsusb

Fortunately, the device was visible. That was the first good news: the system saw the reader at the hardware level. The problem lay somewhere higher up.

Step 2: The missing driver, i.e. the main culprit

I started digging deeper and found out that the ACS reader requires an additional acsccid driver, which works with the pcscd service. Without it, the system sees the device but cannot communicate with it. I found the driver on the ACR39U Smart Card Reader page.

First, I made sure the PC/SC service itself was installed:

sudo apt update
sudo apt install pcscd

Then I downloaded the driver from the manufacturer's website. For my distribution — Zorin OS 17.3 (equivalent to Ubuntu 22.04, Jammy) — it was the libacsccid1_1.1.13-1~bpo22.04.1_amd64.deb package.

Installation in one command:

sudo dpkg -i libacsccid1_1.1.13-1~bpo22.04.1_amd64.deb

And finally, a service restart:

sudo systemctl restart pcscd

That was basically the whole secret. One missing driver and one restarted service.

Step 3: The application finally works

I launched proCertum SmartSign from the terminal (I had already installed the application earlier):

/opt/proCertumSmartSign/proCertumSmartSign.sh

The application started and… saw the key. For the first time in ages. Everything went automatically.

Signing a test document — a PDF payment form — went smoothly. PIN, confirmation, done. No errors, no daylight saving time warnings or other strange logs.

Lessons for posterity

It turns out that the response from technical support two years ago missed the point. The problem wasn't Gnome, but the reader driver that no one mentioned. If I had known about acsccid back then, I would have saved myself a lot of frustration.

So if you're facing the same problem as me — Linux, proCertum SmartSign, ACS ACR39U reader, and the application doesn't see the key — just check if you have the libacsccid1 driver installed and if the pcscd service is running. The rest will be downhill.

After years of struggle: victory. And in spite of technical support.