Microsoft confirms UEFI fears, locks down ARM devices

By Aaron Williamson | January 12, 2012

At the beginning of December, we warned the Copyright Office that operating system vendors would use UEFI secure boot anticompetitively, by colluding with hardware partners to exclude alternative operating systems. As Glyn Moody points out, Microsoft has wasted no time in revising its Windows Hardware Certification Requirements to effectively ban most alternative operating systems on ARM-based devices that ship with Windows 8.

The Certification Requirements define (on page 116) a “custom” secure boot mode, in which a physically present user can add signatures for alternative operating systems to the system’s signature database, allowing the system to boot those operating systems. But for ARM devices, Custom Mode is prohibited: “On an ARM system, it is forbidden to enable Custom Mode. Only Standard Mode may be enable.” [sic] Nor will users have the choice to simply disable secure boot, as they will on non-ARM systems: “Disabling Secure [Boot] MUST NOT be possible on ARM systems.” [sic] Between these two requirements, any ARM device that ships with Windows 8 will never run another operating system, unless it is signed with a preloaded key or a security exploit is found that enables users to circumvent secure boot.

While UEFI secure boot is ostensibly about protecting user security, these non-standard restrictions have nothing to do with security. For non-ARM systems, Microsoft requires that Custom Mode be enabled—a perverse demand if Custom Mode is a security threat. But the ARM market is different for Microsoft in three important respects:

  • Microsoft’s hardware partners are different for ARM. ARM is of interest to Microsoft primarily for one reason: all of the handsets running the Windows Phone operating system are ARM-based. By contrast, Intel rules the PC world. There, Microsoft’s secure boot requirements—which allow users to add signatures in Custom Mode or disable secure boot entirely—track very closely to the recommendations of the UEFI Forum, of which Intel is a founding member.
  • Microsoft doesn’t need to support legacy Windows versions on ARM. If Microsoft locked unsigned operating systems out of new PCs, it would risk angering its own customers who prefer Windows XP or Windows 7 (or, hypothetically, Vista). With no legacy versions to support on ARM, Microsoft is eager to lock users out.
  • Microsoft doesn’t control sufficient market share on mobile devices to raise antitrust concerns. While Microsoft doesn’t command quite the monopoly on PCs that it did in 1998, when it was prosecuted for antitrust violations, it still controls around 90% of the PC operating system market—enough to be concerned that banning non-Windows operating systems from Windows 8 PCs will bring regulators knocking. Its tiny stake in the mobile market may not be a business strategy, but for now it may provide a buffer for its anticompetitive behavior there. (However, as ARM-based “ultrabooks” gain market share, this may change.)

The new policy betrays the cynicism of Microsoft’s initial response to concerns over Windows 8’s secure boot requirement. When kernel hacker Matthew Garrett expressed his concern that PCs shipped with Windows 8 might prevent the installation of GNU/Linux and other free operating systems, Microsoft’s Tony Mangefeste replied, “Microsoft’s philosophy is to provide customers with the best experience first, and allow them to make decisions themselves.” It is clear now that opportunism, not philosophy, is guiding Microsoft’s secure boot policy.

Before this week, this policy might have concerned only Windows Phone customers. But just yesterday, Qualcomm announced plans to produce Windows 8 tablets and ultrabook-style laptops built around its ARM-based Snapdragon processors. Unless Microsoft changes its policy, these may be the first PCs ever produced that can never run anything but Windows, no matter how Qualcomm feels about limiting its customers’ choices. SFLC predicted in our comments to the Copyright Office that misuse of UEFI secure boot would bring such restrictions, already common on smartphones, to PCs. Between Microsoft’s new ARM secure boot policy and Qualcomm’s announcement, this worst-case scenario is beginning to look inevitable.

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