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I have a three-week old laptop with the following entry in the UEFI dbx database:

EFI_CERT_SHA256_GUID

Is this a reference to the hashing algorithm used for dbx entries, or an actual entry (and therefore something to be concerned about)? I'm asking because I will be disabling secure boot and installing an OS in CSM mode, and wouldn't want to do so if there is already a entry in the dbx.

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If you're disabling Secure Boot completely, then it shouldn't matter. –  nhinkle Jul 15 '13 at 23:40
    
Perhaps I've misunderstood. If there is an entry in the dbx, doesn't that mean that the BIOS is compromised? –  user238358 Jul 16 '13 at 0:17
    
My understanding (and admittedly I am not an expert, but I've done some research) is that if a key is in the dbx then it cannot be used if secure boot is enabled. If secure boot is turned off, then it won't have any impact. Having a key in the dbx doesn't mean that UEFI is compromised, it might mean that the manufacturer had an old key that they've blacklisted or any of a number of other possibilities. –  nhinkle Jul 16 '13 at 0:21
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It's a samsung np900x3c. I'm going to put Linux on it, but am unwilling to try with UEFI as there are lots of documented cases of samsung laptops becoming bricked when trying to boot Linux in UEFI mode. –  user238358 Jul 16 '13 at 2:07
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That's probably smart. See if you can find any documentation for your specific laptop, but the best bet would probably be to disable secure boot completely, and if you have the choice, put it into legacy BIOS mode and disable UEFI, just to be safe. On most laptops UEFI+Secure Boot+Linux isn't a problem (if the distro is signed) but with Samsung's recent issues it's probably wise to be careful. –  nhinkle Jul 16 '13 at 2:14
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