Knox is the security precaution behind Samsung now. Its just basically saying you rooted your phone. Does your phone come with a locked bootloader or are you unlocked by default? Knox will also stop you from downgrading. If you try your phone is straight dead... But you should be able to use safesteap I think.... I think safe strap is out for this one. I can see if I can find it if you would like...
Sent from my Rezound using xda-developers app. CyanogenMod 11. S-off
HTC Rezound: Cyanogenmod 11, Liquid Smooth 2.37, Sense 4 and 5
S-OFF using Rumrunner.
TWRP: 22.214.171.124 with The RAVEN Theme
iPad 1st Generation Jailbroken with Green pois0n . iOS 5.1.1
Droid Incredible: Stock (not for long hehe)
HTC EVO 4G the Original OG 4G: AOKP 4.2.2 ;D