Howto upgrade Lenovo G50-45 80E3 under linux? Not there yet!
Cut off the first 2912 bytes and make the file 8MB, 2912 = B60 in hex.
dd if=Win213.bin of=Win213-unsigned.bin bs=32 skip=91 count=256k
md5sum Win213-unsigned.bin 
a32065e67f7c5d3830911bb57e3f907b  Win213-unsigned.bin

This is the unsigned UEFI file.

sudo ./H2OFFT-Lx64 Win213-unsigned.bin -SB
                        New BIOS Model Name : Mullins-LarneML
                        New BIOS Version    : A2CN45WW(V2.13)
                        New BIOS Build      : 08/05/2016 10:02:46

                        
Of course this can't be flashed successfully:
I'm using: Tool IHISI version: 2.0.2

sudo ./H2OFFT-Lx64 Win213-unsigned.bin

                       Please do not remove the AC power 



         Insyde H2OFFT (Flash Firmware Tool) Version (SEG) 100.00.07.21
      Copyright(c) 2012 - 2015, Insyde Software Corp. All Rights Reserved.



                        Initializing

                        File loading    100 %  

               Current BIOS Model name: Mullins-LarneML
               New     BIOS Model name: Mullins-LarneML

               Current BIOS version: A2CN23WW(V1.05)
               New     BIOS version: A2CN45WW(V2.13)


Error: It only supports to flash secure BIOS on current platform.
The image to be updated is not a secure BIOS. 

platform.ini and messages.ini are also included in the Win213.bin file from Lenovo.