[U-Boot] U-boot changes

Hi, I am trying to perform secure booting on nitrogen6x SOM.After compiling the u-boot2013.08 source code I have obtained a u-boot.imx image with fsize 51c00.I tried to pad and sign this image for authentication which returns me a u-boot-signed-padded.imx. The problem is that the size of this new image is still the same i.e 51c00 which impiles that actually no change is happening to u-boot.imx. I tried making some chage u-boot.lds file to attach HAB data but it did not work.How can this problem be solved?

Thanks in Advance!