Exploring the Security Vulnerabilities of EM4100 RFID-Based Access Control Systems

Hacking electronic turnstiles at the entrance to the building is a cherished hacker flex that is so loved to be shown in movies. In this article, we will explore the security vulnerabilities of RFID-based remote access control systems (ACS), and together we will figure out how easy it is to fake the most common EM4100 ID.

What is an ACS?

ACS (Access Control System) is a set of equipment designed to restrict access to a protected facility. The minimum configuration of such a system is an RFID-based electronic lock.

What is RFID?

RFID (Radio-Frequency Identification) is a method for automatically identifying objects using radio signals stored on transponders (RFID tags). RFID tags are prefabricated devices for storing information, consisting of an integrated circuit (chip) for performing operations with a signal and information, an antenna for transmitting and receiving a signal, and, optionally, a battery (not common in everyday use – expensive and redundant).

What is EM410X?

EM410X is an extremely popular ID model line developed by EM Microelectronics. In everyday life, they are used in a variety of ways: from the use of state (and not only) institutions in the access control system to the marking and accounting of animals. This includes chips with IDs EM4100, EM4102, EM4105 and EM4200, which differ in memory size (from 64 to 128 bits) and applications.

How is the EM4100 Arranged?

The data structure in the EM4100 identifier is as follows. The most important for us in this scheme is a group of blue and blue bits, which together make up 5 bytes (40 bits) and serve as a unique identification code for an RFID tag.

Attack Vectors on ACS with EM410X

None of the variations of the EM410X has cryptography or some other method of protection. Therefore, all the attack vectors that can be detected are either related to the fundamental shortcomings of the identifiers themselves, or to their unsafe operation.
As an attack target, let’s consider a stand-alone (not integrated with other systems) ACS with contactless readers. This is the easiest option to understand and reproduce the attack.
So, our goal is to get at least one access token that can be used to open the door. To do this, we need to know the structure of the EM4100 identifier and the way it works.