Hack Your Access Control With This $30 HID 125kHz Card Copier

Many access control systems that allow 125kHz cards can be easily hacked by a cheap $30 card copier. We overview this risk in the video below:

And this technical video below shows the steps in greater detail:

In our tests, we copied multiple 125 kHz formats and tested them on multiple readers. While very inexpensive, the card copier did not malfunction or create corrupted copies in any of the 15+ cards we copied.

The Big Risk

Indeed, to access control systems, these copies look identical to legit cards.

The test screenshot below, shows that card copies are indistinguishable from the HID factory original:

The risk is that unauthorized copies can be made and used to gain access, with no outward sign or record of being a duplicate.

Formats Matter

One specific caveat to this test: not all card types and formats are at risk. This particular tool can be used to copy 125kHz card types, including popular HID Prox, ISOProx, and Prox II formats, and several others commonly used in access control such as EM4100 and AWID formats.

Specifically, this tool cannot copy any 13.56MHz 'Smartcard' formats like the latest HID iClass, or DESFire/MIFARE varieties. One of the major differences between those formats is 13.56MHz formats are encrypted and the data they hold must be first decoded by the companion reader with a specific 'key' value, otherwise, the information they transmit in the open air is heavily hashed and obscured.

However, most 125kHz formats are simply not encrypted at all. This means the process of copying them simply energizes the card, and stores the information it broadcasts. Card details are stored on the card exactly as the system uses them, so sensitive card numbers and facility codes are easy to pull from thin air.

Vulnerable 125 kHz Common

Despite the risks of unsecured 125 kHz cards and fobs, they are commonly used and even preferred by many installers and end-users.

In our Favorite Access Control Credentials 2020, those vulnerable types still command 14% of the favorite votes:

Indeed, these credentials vulnerable to copiers are still used in tens of thousands of systems, with millions of issued credentials circulating every day.

Cheap & Easy To Get

The copier we tested was purchased for $30 shipped. Overall, the price of the unit tested was slightly higher due to the configuration of copying HID formats, but units as low as $10 can be purchased to copy basic EM4100 formats alone.

The kit we purchased was shipped with several blank re-writable keyfobs but we also purchased a box of 50 blank cards, so the material cost for this exploit is less than $45.

The chilling lesson is these products are very inexpensive, readily available, and sold by multiple vendors eager to ship the next day with no questions asked for anyone, crook or honest.

How It Works

The device used to copy the cards works much the same way as normal card readers, with transceiver coil, power supply, IC chip, buzzer, and even LEDs components shared by both:

Given the principal operation of contactless card readers, the copier excites the coil and delivers power wirelessly to the card, which then momentarily stores energy and then uses it to broadcast card details back to the copier. The image below shows a transparent example of a card, revealing all these components:

The copier includes a small amount of memory to store those details, and then pushes them to a blank card, writing them permanently as a copy.

Near Contact Required

One particular factor of this unit is cards to be copied must be held close to the copying antenna to work, a distance of less than 1". This is somewhat a benefit to cardholders because someone bent on stealing and spoofing card details must be very close to accomplish it.

However, the time needed to steal the information is fast - less than 5 seconds, and it is conceivable that someone could have card details copied and stolen without realizing it, especially in crowded groups of people.

But the method used by this device is available in other forms functional at longer distances - some claiming 5 feet range or more and often using modified off-the-shelf long-range readers:

These longer-range copiers are much more expensive ($500+ vs. $30), physically larger, and require more power than 2 AA batteries. However, carrying the components covertly in a backpack or briefcase means that those stealing cards can just blend in better with crowds.

Mitigating This Risk

So what can be done to prevent this exploit? The most straightforward step is to discontinue using HID (or any) 125 kHz cards, fobs, and readers and switch to encrypted and hashed 13.56 MHz formats.

Breaking down the three options, the most secure and fastest but highest cost and system impact method is the immediate replacement of both 125 kHz readers and user cards, while the least expensive but potentially slow and most vulnerable method is simply mounting a 13.56 MHz reader aside existing units and begin rotating new cards to users as needed.

The best mix of low cost, meaningful security improvement, and low system impact is to use a replacement reader that can scan multiple card frequencies and formats, often called 'multi-function' readers. This chart shows the trade-offs:

For more details, see our Hackable 125kHz Access Control Migration Guide.

[NOTE: This report was originally published in 2017 but was revised and a new video was added in 2021.]