Provided you have a recent USBNet build installed, does this work?
Code:
cd /mnt/us
kindletool convert -kws Update_mkk-20140214-k5-ALL_install.bin
openssl dgst -sha256 -verify /etc/uks/pubdevkey01.pem -signature Update_mkk-20140214-k5-ALL_install.psig Update_mkk-20140214-k5-ALL_install_unwrapped.bin