Can Interchangeable Cores Be High-Security?

Jan. 3, 2019
Interchangeable Cores now give you a broad range of options to upgrade and extend existing systems, as you add legal, mechanical, and electronic security enhancements

The overwhelming prevalence of Interchangeable Cores in large institutions raises the following questions. How secure are Interchangeable Cores? What security options do you have? Today, convenience and security are not mutually exclusive. Your challenge is to help the customer clearly understand what net benefits they are actually getting for their high security investment.

High Security was originally defined by the UL 437 standard which covered lockpicking, impressioning, and destructive entry.   The more recent BHMA/ANSI A156.30 specifies standards for (external) Key Control, Destructive Tests, and Surreptitious Entry. This later standard covers a wider variety of issues, including key availability (during the patent period), and electronic equipment and attacks. It does not however, deal with the important issue of customer-managed post-install key control. Search for: ANSI_BHMA_A156.30_2014.pdf  

In the real world, keys are lost, stolen, loaned, and copied. Departments expand, move and contract. Staff is hired, promoted, moved, and departs. All of these events lead to the 20 percent annual decline of internal key control.

The Interchangeable Core was developed to help solve these post-installation key control problems. Entire buildings or wings could be pinned in-shop, and then field-installed in minutes. With good record keeping and periodic key audits, external key duplication was minimized.

Gradually, all major hardware companies created their own Interchangeable Cores. Each was designed to allow customers to migrate from existing keying systems to an interchangeable version for cost-effective system maintenance. Although these products all have their own distinct locking lug, pinning, and size variations, they are collectively called Large Format Interchangeable Cores (LFIC). The original Best figure eight SFIC core became the industry standard, and is available from all domestic producers.

Builder’s hardware companies Arrow®, Best®, Falcon®, Corbin Russwin®, Sargent®, Schlage®, and Yale® focus on the “spec and bid” new construction market with full lines of door hardware and with various high security I-Cores. Existing customers want good “specs” that help them maintain keying system continuity. This can be an important customer satisfaction issue.

High security aftermarket solutions are provided by CX5, plus the Medeco® and ASSA divisions of ASSA ABLOY. CX5 and Medeco provide both large and small format high security options, while ASSA currently offers only LFIC versions. Best originally focused on converting large institutional keying systems to the SFIC, but in recent years has become a strong player in the new construction market as well.

For many years, limited key availability and tight tolerances helped keep SFIC systems secure. Bootleg keys just didn’t work very well – if at all. Seven-pin close tolerance SFIC cores could be picked or bumped by skilled practitioners, but it was exponentially more difficult and rarely seen, as additional security measures were generally in place. Consistent internal key control processes and key audits also helped defend against unauthorized keys.

Electronic Access Control (EAC) at portals has added an important level of accountability and flexibility to lock systems, while video has dramatically reduced unobserved attack time. Restricted or patented keys reduce external availability, but don’t address the many other serious problems of internal change and loss. Ultimately, as prices come down, we may see hybrid electronic credentials like ASSA ABLOY’s CLIQ®, the ABUS RFID Combi Cap, or your own mobile phone gain wide market acceptance, providing instant continuous key control.

From the late 1960s through the 80s, Medeco pioneered pick and tamper-resistant locks, and later successfully promoted the concept of patents limiting exterior access to bootleg keys. The inevitable result was that market forces would merge the Interchangeable Core, limited access key blanks, and defeat resistant cylinders and locks. These trends increased demand for higher security levels for all players in the huge Interchangeable Core market.


A number of recent innovations by OEM hardware manufacturers and aftermarket specialists provide patented keying, pick, tamper and bump resistance, and in some cases high levels of physical attack resistance. The drawback of the SFIC is that its smaller size doesn’t provide as much room for multiple mechanical or electronic devices within the core itself.

The LFIC, by virtue of its larger size, has more room for additional levers, pins, sidebars, and electronic devices. The disadvantage of the LFIC is that each brand has its own size, locking lug, and pinning system, preventing LFIC standardization. The major players in the I-Core market are as follows.

ABUS Pfaffenhain has developed a very sophisticated I-Core (2034 patent), and RFID key attachment, but have not yet integrated these into existing North American I-Core housings.

The Schlage® division of Allegion provides both SFIC and LFIC core options. Schlage uses the term “Full Size Interchangeable Core” (FSIC). The Everest 29 (2029 patent) uses a secondary undercut key to lift a check pin, allowing plug rotation. Many of these are backward compatible with existing Schlage or with A2 systems. Schlage’s Primus® XP LFIC (or FSIC) cores utilize additional finger pins to control a locking sidebar, and has geographically exclusive side-bit key milling options. These Primus XP LFIC cores are available with UL 437 listed cylinders.

The Schlage Small Format Interchangeable Core (SFIC) comes in the 7-pin Everest 29TM R keyway. Thse cores can be used on a mixed cylinder campus with the SL cylinder options that share the R keyway and enable an upgrade to Primus XP levels of security with the LFIC core.

ASSA ABLOY has acquired several North American lock companies including; Arrow, Corbin Russwin, Medeco, Sargent, and Yale, in addition to other physical security acquisitions. The Medeco and ASSA divisions remain focused on the aftermarket while the other OEMs concentrate on “spec and bid” new construction.

The Arrow™ division of ASSA ABLOY produces conventional and SFIC cores. The classic Pointe SFIC core is augmented with the Pointe Flex system containing a pin at the bottom of the keyway blocking unauthorized key blanks. The Choice system is no longer shown on the Arrow website.

ASSA maintains its North American offices at the Sargent facility in New Haven, CT. For a review of the full line of ASSA LFIC cores and products, download the ASSA Catalog:

Corbin Russwin offers a robust Large Format Interchangeable Core available with their Pyramid Security and High Security systems. The Pyramid systems contain a secondary bottom blocking plate and are available in 20 keyway sections.  Pyramid key patents expired in 2018, and have been replaced with the Access 3® system (2027 patent). The entry level AP system provides patented keys and bump resistant pins. The mid level AS system adds angled bottom pins, side bar, and geographical exclusivity. The highest AHS level meets UL 437 standards.

Sargent provides three security levels of the Degree® system (2027 patent), and also the Keso F1 (2024 patent) with side dimple keying. The Degree DG1 LFIC system provides patented keys and a bump resistant side bar. The DG2 system adds chisel point bottom pins and a bottom slider bar. The DG3 system adds the UL 437 rating when mounted in appropriate housings. The legacy Signature system (2012 patent) uses two bottom blocking bars and side pins to enhance tamper resistance and is available in UL 437 configuration in LFIC core format only. Electronic access control can also be added to the Degree system with ASSA’s CLIQ hybrid system. Info:

Medeco® specializes in high security Large and Small Format I-Cores and cylinders for a wide range of other brand locks, as well as building their own high security lines. Recent years have seen the addition of the electronic XT access control product as well as ASSA’s CLIQ electronic hybrid key.

Medeco3 (M3) LFIC cores (2027 patent) use the familiar Biaxial technology with an additional patented slider and sidebar. The slider is moved into a precise position to allow the sidebar to retract. These LFIC cores are certified to UL 437 standards (when installed in appropriate housings). M3 cores are available to fit all LFIC formats including: ASSA, Corbin Russwin, Sargent, and Yale, as well as Medeco’s own LFIC format. The patented X4 keying system is also available in these LFIC cores as well as SFIC.

The company has moved aggressively into the Small Format Interchangeable Core market with three product lines to serve this large market. The MedecoB SFIC line is available in 6 or 7-pin cores in all popular unpatented keyways. These “B” SFIC cores are available though authorized distributors and do not require purchase contracts.

The X4 series (2027 patent) adds spool pin segments and a bottom locking pin to improve tamper resistance and patent protection.

The XT provides electronic options that allow your customer to perform normal EAC functions in existing SFIC or LFIC housings. The user credentials contain long-life battery power and become the link to the central database. The CLIQ mechanical-electronic hybrid system’s key can also operate M3 LFIC and standard cylinders, but not SFIC.

 Yale offers the KeyMark® keying system with security leg and spool pin segments available, as well as the legacy 5000 series. The KeyMark system is available in Large and Small Format Interchangeable cores.

Best® Access Systems developed the original interchangeable core. They are now a division of the Swiss dormakaba group, along with Precision Hardware (PHI®), and Stanley® hinges.

In recent years, Best partnered with Kaba to provide the Peaks® system, and later the Peaks Preferred® (2024 patent). The Best COREMAX (2027 patent) uses a simple but effective rear pin to prevent core rotation unless the properly milled side cut is present. COREMAX SFICs also contain spool and hardened steel pin segments as well as the locking pin to further enhance attack resistance.

The Best 5C SFIC core with double side locking lugs is used with the 1E7J4 high security cylinder. The hardened cylinder completely covers the SFIC core with extreme attack and tamper resistance, but is changed in seconds with the standard longer blade control key. The double locking lugs, extra large cylinder set screw, internal secondary set screw, and drill, bump, pick and pull protection allow this SFIC assembly to meet UL 437 standards when installed in the 47H high security mortise lock..

CX5 is a Montreal based company that produces both LFIC and SFIC cores with spool pins, a secondary internal set screw, and more than 60 sidebar configurations per keyway. The finger pins are factory installed, and do not require removal for re-pinning with the standard A2 or A4 pinning kit.

Key duplication has been a non-issue due to geographical restrictions, number of sidebar options, and prohibitive tooling cost. Ease of maintenance, pick and tamper resistance, and restricted distribution make this an interesting option for both LFIC and SFIC systems.

Cyberlock® is the other player in this market with it’s battery powered CyberKey® and Flex System™ that allows mechanical, CyberKey, and other electronic access systems to integrate. Best style SFIC and Schlage style LFIC cores are currently available.

Security management theory has for some time held that multiple layers of protection are far more effective than a single “Maginot line,” which Encarta calls “an ineffective defensive strategy that is relied on with unthinking confidence.” We’ve all seen examples of overreliance on a single device or technology that gets bypassed in ways not previously considered.

As a practical matter, increased pick and tamper resistance is usually applied to unobserved or high value openings while less complex I-Cores are more cost-effective for the many hundreds of other less critical doors. Best practices will back up high risk openings with CCTV, intrusion alarms and electronic access control systems, rather than reliance on a potential single point of failure.

Interchangeable Cores now give you a broad range of options to upgrade and extend existing systems, as you add legal, mechanical, and electronic security enhancements. As with everything, keep the customer’s interest foremost in your mind and you will have a long and much more profitable relationship.

Cameron Sharpe, CPP wrote for Caterpillar and Honeywell before working 25-years in hardware and electronic access distribution. [email protected]   Copyright © 2018

About the Author

Cameron Sharpe

Cameron Sharpe, CPP, worked 30 years in the commercial lock and electronic access industry. Contact him at [email protected].