can't root Acer iconia tab 8

[SuperWind]

I have the Iconia Tab 8 and when I try to flash SuperSU update zip to root my tab in recovery mode I keep getting the Signature Verification error and E:Error in /cache/sideload/package.zip how do I fix this please help me.

 

[funkylogik]

Are you using a custom recovery (twrp, cwm, philz)?