OSDP: Making Weigand Look Like Magstripe

Access control systems don’t fail because technology stops working. They fail because outdated assumptions quietly persist.

In this episode of Vigilant By Design, host Benjamin Johnson, CPP, PSP, PMP, takes a deep dive into the evolution of access control reader communication protocols — Clock & Data, Wiegand, and OSDP — and explains why this often-overlooked layer is one of the most important trust boundaries in physical security.

We explore:

• How Clock & Data originated in early magnetic stripe systems and why simplicity came at the cost of security

• How Wiegand became the industry standard, what the Wiegand effect actually is, and why compatibility outlived protection

• Exactly how these protocols work at the signal level, including wiring, voltages, and communication models

• The fundamental security limitations of one-way, unencrypted reader communication

• Why credential data, device trust, and supervision matter in modern threat environments

• How OSDP was designed to replace assumption-based trust with verification through bi-directional communication, encryption, and supervision

• When legacy protocols may still be acceptable — and when they represent unnecessary risk

This episode connects access control technology history to modern realities, including insider threat, credential cloning, AI-enabled impersonation, and long-term system design.

Clock & Data trusted the wire.
Wiegand trusted the reader.
OSDP verifies both.

If you are responsible for security decisions, system design, or long-term infrastructure planning, this episode will help you understand not just what works — but what deserves trust.

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