In the early 1990s, proximity card technology represented a genuine breakthrough for physical access control. For the first time, building occupants could gain entry by simply holding a credential near a reader—no insertion, no swiping, no physical wear and tear. The convenience was revolutionary, and 125 kHz proximity cards rapidly became the industry standard.
Three decades later, that same technology has become one of the industry's most significant vulnerabilities. Understanding how we arrived at this point requires looking at both the original promise of proximity technology and the security landscape that has evolved around it.
To appreciate why proximity cards seemed so transformative, you need to understand what came before them.
Throughout the 1980s, magnetic stripe cards dominated access control systems. These cards required physical contact with card readers—users had to insert or swipe their cards through reader mechanisms to gain entry. While this approach worked, it created several persistent problems:
Physical wear: The constant friction between cards and readers degraded both over time, requiring frequent replacement of cards and expensive maintenance of reader mechanisms.
Slow throughput: In high-traffic locations, the need to properly align and swipe cards created bottlenecks, particularly during shift changes or busy entry periods.
User frustration: Cards frequently failed to read properly, forcing users to swipe multiple times or seek assistance from security personnel.
Demagnetization vulnerability: Magnetic stripe cards could lose their encoded information when exposed to magnetic fields, rendering them useless without any visible damage. This is the classic “don’t put your hotel keycard next to your phone” warning!
For facility managers and security directors in the late 1980s, these weren't minor inconveniences—they represented significant operational costs and user experience problems that demanded a solution.
The development of Radio Frequency Identification (RFID) technology in the 1990s offered an elegant answer to the magnetic stripe problem. Proximity cards operating at 125 kHz could communicate with readers from several inches away, eliminating physical contact entirely.
The advantages were immediately apparent:
Durability: Without physical contact, both cards and readers lasted significantly longer, reducing replacement and maintenance costs.
Speed: Users could authenticate and pass through doors much more quickly—critical for large facilities with high traffic volumes.
Convenience: Cards could remain in wallets, purses, or pockets. Users simply held their entire wallet near the reader rather than removing and inserting a specific card.
Form factor flexibility: The technology enabled credentials in multiple formats—cards, key fobs, and tags—giving organizations options for different use cases.
For organizations managing large facilities, university campuses, corporate offices, or manufacturing plants, the operational improvements justified the investment in new infrastructure. Proximity cards rapidly became the industry standard throughout the 1990s and early 2000s.
Here's what few organizations fully appreciated at the time: proximity cards achieved their convenience through fundamental security trade-offs.
The 125 kHz technology that made proximity cards so practical also imposed severe constraints:
Low frequency, limited data: Operating at 125 kHz meant proximity cards could only transmit small amounts of data—typically just a facility code and card number, usually totaling 26 bits of information.
No encryption: The limited data capacity meant proximity cards transmitted their credentials in plain text with no encryption whatsoever.
One-way communication: Readers could receive signals from proximity cards, but cards couldn't authenticate readers in return—no mutual authentication existed.
Passive technology: Proximity cards contained no power source or processing capability, just a simple antenna and integrated circuit that responded to the reader's radio field.
In the security context of the 1990s, these limitations seemed acceptable. After all, someone would need physical access to a card, specialized equipment to read it, and knowledge of the facility's access control system to exploit the vulnerability. The barrier to entry seemed high enough… at the time.
But technology evolves—and not always in the direction security professionals anticipate.
The first cracks in proximity card security appeared in the early 2000s, as security researchers began demonstrating how easily 125 kHz cards could be cloned. What required specialized equipment and technical knowledge in the 1990s became increasingly accessible. Wavelynx demonstrates that in this modern era, you can clone a proximity card in less than 5 seconds with no prior technical knowledge and a “equipment spend” of less than $20 on Amazon.
By the 2010s, the tools and knowledge needed to clone proximity cards had become widely available:
Commodity hardware: RFID readers and writers capable of capturing and duplicating proximity card data became available through mainstream online retailers for less than $20.
Simplified software: User-friendly applications eliminated the need for technical expertise, making card cloning accessible to non-technical users.
Distance reading: Attackers discovered they could capture proximity card data from several feet away using amplified readers—far beyond the official reading range.
Online documentation: Step-by-step instructions for cloning proximity cards proliferated across forums, video platforms, and security blogs. Not that you really need these instructions, though.
The emergence of devices like the Flipper Zero in the 2020s represented the culmination of this trend. As noted by HID's own director of business development, these portable devices render 125 kHz proximity cards "not just obsolete, but actually dangerous"—they've made credential cloning so accessible that the security model underlying proximity cards has fundamentally collapsed.
Ironically, one of proximity technology's greatest strengths became one of its most significant weaknesses: interoperability.
Because 125 kHz proximity technology became so ubiquitous, the industry developed broad interoperability across different manufacturers' cards and readers. This created genuine value—organizations weren't locked into single vendors, and the competitive market drove prices down while improving quality.
But that same interoperability meant that anyone with basic RFID equipment could read, copy, and reproduce proximity credentials regardless of which manufacturer produced the original card. The lack of encryption and authentication that made interoperability simple also made security impossible.
This created a dilemma that persists today: organizations need interoperability for flexibility and cost control, but the kind of interoperability that proximity cards offered came at the expense of security. Finding the balance—security through encryption combined with interoperability through open standards—became the challenge that would eventually drive the industry toward modern credential technologies, and thus proprietary vendor lock-in.
The security vulnerabilities of 125 kHz proximity cards weren't news to the access control industry. First-generation smart cards emerged around 2000, operating at higher frequencies (13.56 MHz) with encrypted credentials and mutual authentication between cards and readers.
So why, 25 years later, do proximity cards remain so prevalent? When the vulnerability is so obvious, and secure options exist, why are over a third of businesses still utilizing prox cards?
The installed base: Organizations had invested heavily in proximity infrastructure. With thousands or tens of thousands of cards deployed and readers at every entry point, the cost of replacement seemed prohibitive. Organizations like rf IDEAS explore and advise on this challenge, especially with the consideration of physical access control and logical access control convergence.
The "good enough" fallacy: Many organizations reasoned that their specific security needs didn't justify the upgrade cost. After all, if proximity cards had worked for years without incident, why change?
The lack of immediate consequences: Unlike network security breaches that generate headlines and regulatory attention, physical access vulnerabilities often remain invisible until they're exploited—and even then, they're rarely publicized.
The transition complexity: Moving to new credential technology wasn't just a matter of buying new cards. It required careful planning, potential reader upgrades, staff training, and coordination across multiple departments.
These factors created a form of institutional inertia. Organizations knew proximity cards were vulnerable, but found reasons to postpone action. The result: almost 40% of credentials sold worldwide continue to be 125 kHz proximity cards, even as the security case against them has become overwhelming.
What's changed to make a transition urgent now rather than simply advisable?
Threat accessibility: The tools and knowledge needed to exploit proximity card vulnerabilities are now in the hands of anyone with internet access and $20, not just sophisticated attackers. Watch it happen in real life, here.
Compliance requirements: Auditors and regulators increasingly view legacy proximity cards as indefensible vulnerabilities, particularly for organizations handling sensitive data or operating in regulated industries.
Breach costs: According to IBM's 2025 Cost of a Data Breach Report, the average data breach costs $4.44 million — and physical access control weaknesses increasingly serve as initial entry vectors.
Insurance implications: Some organizations are discovering that their cyber insurance policies contain exclusions for breaches enabled by known vulnerabilities, including outdated access control technology, such as proximity credential technology.
Reputation risk: In an era where organizations tout their security practices, maintaining obviously vulnerable access control systems creates both actual risk and reputational exposure.
Perhaps most importantly, the transition path has become clearer. Modern credential technologies, such as the LEAF Framework, offer both security and the kind of interoperability that made proximity cards attractive in the first place—but through universal standards and encryption rather than through lack of security.
The proximity card story offers important lessons for how organizations approach security technology transitions:
Convenience and security aren't opposites: The proximity card era taught the industry that users won't accept security that creates friction. Modern solutions must deliver both security and user experience.
Interoperability remains essential: Organizations must have the flexibility to choose best-of-breed solutions, which runs contrary to a vendor lock-in approach. The answer isn't returning to proprietary systems—it's achieving interoperability through secure, universal standards.
"Good enough" rarely is: What seems like acceptable risk today becomes an obvious vulnerability tomorrow as technology evolves. Security decisions should consider not just today's threat landscape but tomorrow's.
Transition costs compound: Every year organizations delay migration from proximity cards, they deepen their dependence on legacy technology, which makes their eventual transition more complex and expensive.
Industry leadership matters: The organizations that have successfully transitioned are those that made security infrastructure a strategic priority rather than waiting for a crisis to force action.
The proximity card era represented genuine innovation. For more than two decades, 125 kHz technology delivered enormous value through improved convenience, reduced operational costs, and better user experience. The engineers who developed this technology solved real problems that plagued earlier access control systems.
But technology exists in context, and that context has changed fundamentally. The security assumptions underlying proximity card technology—that cloning would require specialized expertise and equipment, that physical credential theft would be obvious, that organizational security postures didn't face sophisticated threats—no longer hold.
The industry has moved on. Modern credential technologies offer encryption, mutual authentication, multi-application functionality, and the ability to integrate with mobile devices—all while maintaining the convenience that made proximity cards attractive in the first place.
The question isn't whether organizations should transition away from 125 kHz proximity technology. The question is whether they'll do so proactively, on their own timeline and terms, or reactively after a security incident forces their hand.
Coming Next: "Planning Your Migration: A Framework for Moving Beyond Prox"
In our next article, we'll examine the technical details of proximity card cloning, the tools attackers use, and why this vulnerability has become so accessible to non-technical threats.
About the LEAF Community
The LEAF Community creates universal standards for access control systems to achieve interoperability across the industry. We bring together leading companies and organizations to overcome vendor lock-in barriers and promote standardized frameworks that allow different access control technologies to work together seamlessly. Learn more at leaf-community.com.
.png){kind=small}
.png)
.png)
