Back to all

Introducing OSDP to Access Control

Access control systems play a pivotal role in safeguarding buildings and facilities, ensuring only authorized individuals gain entry while keeping unauthorized persons at bay.

Integrated security | 15/04/2024

Understanding OSDP: Enhancing Access Control Systems

Access control systems play a pivotal role in safeguarding buildings and facilities, ensuring only authorized individuals gain entry while keeping unauthorized persons at bay. At the heart of modern access control lies OSDP – the Open Supervised Device Protocol. In this blog, we delve into the intricacies of OSDP, uncovering its significance, functionalities, and why it’s a game-changer in physical security.

What is Open Supervised Device Protocol (OSDP)?

OSDP [1] serves as the foundation for seamless communication between control panels or security management systems and peripheral devices like card readers, keypads, and biometric readers. Unlike its predecessors such as [2] Wiegand, [3] RS232, [4] BACnet, OSDP sets the bar high with bi-directional communication, bolstering the system’s security, reliability, and interoperability.

The Three Critical Components of OSDP

  1. Access Control Systems: These systems oversee access permissions, log entry/exit activities, and with OSDP, ensure secure and efficient data exchange between supported systems like NetBox and OnGuard.
  2. Readers: From card readers to biometric devices, readers capture user data and relay it to the controller for processing.
  3. Controllers: Serving as the brains behind the operation, controllers manage communication between readers and other devices, dictating access to various areas within the facility.

OSDP vs. Wiegand: A Paradigm Shift in Communication

While Wiegand relies on outdated one-way communication, OSDP revolutionizes access control with:

  • Protocol: Utilizing the robust RS485 protocol for secure data transmission, OSDP trumps Wiegand’s susceptibility to interference and security vulnerabilities.
  • Wires: OSDP streamlines communication with a two-wire system, whereas Wiegand relies on multiple wires, increasing complexity.
  • Encryption: OSDP ensures data security with encryption [5](AES-128), a feature absent in Wiegand.
  • Supervision: Unlike Wiegand, OSDP constantly monitors communication, ensuring system availability and integrity.
  • Transmission: OSDP guarantees successful data transmission with acknowledgments, unlike Wiegand’s lack of assurance.

Understanding OSDP Profiles

The OSDP Profiles represent operational modes that portray specific functionalities within the protocol framework. These profiles, crafted by the Security Industry Association [6] (SIA), establish a standardized avenue for diverse devices and systems to interact, ensuring seamless interoperability and compatibility.

  • Basic: These devices serve as direct replacements for Wiegand protocols while offering the added benefit of bidirectional communication. This bidirectional protocol safeguards against common person-in-the-middle attacks, where unauthorized individuals intercept and tamper with communication data between devices.
  • Secure: Devices meeting Basic profile criteria and capable of managing encrypted messages through Secure Channel are indispensable for ensuring communication safety and privacy. These devices seamlessly transition between Basic and Secure modes, ensuring a smooth and secure user experience.
  • Smart Card: These devices facilitate the exchange of structured data units crucial for smart card operations. They prove invaluable across various settings, including Federal Identity, Credential, and Access Management, as well as Personal Identity Verification contexts.
  • Biometric: Devices like fingerprint scanners or facial recognition systems are gaining popularity for bolstering security measures. Many of these devices leverage OSDP messages to access and compare biometric templates, enhancing overall security protocols.


Benefits of OSDP

  • Enhanced Security and Encryption: AES-128 encryption, supervision of data wires, and tamper alerts fortify security.
  • Automatic Tamper Alerts: Detects and notifies users of physical tampering, bolstering system integrity.
  • Remote Updates: Enables remote configuration and firmware updates, enhancing system management.
  • Efficient Deployment: Simplifies installation with a two-wire system, centralized management, and multi-drop support.
  • International Standards: Recognized globally by reputable industry associations like SIA, ensuring compatibility between different security devices.

Best Practices for Implementing OSDP

  1. Install End of Line Terminating Resistors: Ensure proper impedance matching for reliable transmission. When termination is not implemented, reflection can occur, causing the voltage to bounce back onto the line and distort the signal.
  2. Use Twisted Pair Wire: Minimize electromagnetic interference for robust data transmission. Any external interference or noise is canceled out by twisting the wires, ensuring reliable and high-quality data transmission.
  3. Utilize Low-Capacitance Wire: By using a low-cap wire, which refers to a wire with a lower capacity for electrical current, it helps reduce potential interference or signal degradation.
  4. Employ Stranded Cable: Stranded cables are made up of multiple smaller wires twisted together, which provides flexibility and durability. This ensures that the cable can withstand frequent movement or bending without breaking. It also provides greater resistance to breaking when terminating wires into a Terminal Block connector. (I.E. Access Control panel)

In conclusion, OSDP emerges as a cornerstone in modern access control, offering unparalleled security, efficiency, and interoperability. By embracing OSDP and adhering to best practices, organizations can fortify their physical security infrastructure, safeguarding assets and personnel effectively in today’s dynamic security landscape.



Marijo Horvat, Integrated Security Sector Manager


[1]   eBook Demystifying OSDP:

[2]  Wiegand communication protocol:

[3]  RS-232 communication protocol:

[4]  BACnet communication protocol:

[5]  Advanced Encryption Standard:

[6]   SIA – Security Industry Association: