A nuclear launch code in the form of numbers is made and its integrity is of highest priority so that it won't go into the wrong hands. Let those codes are ($12, S45, $09, $OB, $49, $0A, $21) is encrypted using a checksum key (As checksum key will only validate the authenticity of codes). 

Part-A: Write a code that will take the above number as an input, store them, and then find the checksum key and validate the authenticity of the key. 

Part-B If codes are changed and going to misuse, how will you detect and stop the launch. If you detect codes are tempered shut all necessary communication that stops the transmission of codes. (hint: use a port as a control port for communication control purpose)