It's early days for secure boot, the new method that Microsoft is using to protect its desktop turf, but it would not be unfair to say that the company has succeeded in showing up the sharply fragmented nature of GNU/Linux.
Secure boot is a feature in the Unified Extensible Firmware Interface, the replacement for the motherboard firmware or BIOS. It has been implemented by Microsoft in a manner that effectively prevents easy booting of other operating systems on machines which have secure boot enabled.
An exchange of cryptographic keys takes place at boot-time so that a system can verify that the operating system attempting to boot is a genuine one, and not malware.
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