hi, was able to encode the message have problem with decode..:

decode('FXGAFVXXAXDDDXGA', 'dhxmu4p3j6aoibzv9w1n70qkfslyc8tr5e2g','cipher') == 'iamgoing'

c e h i p r

F A V A D G X F X X D A G X D X

dont know how to divide the sorted header with the encoded message because it can be 2 or 3 char long for the first 5 letters FXGAF (from FXGAFVXXAXDDDXGA) it can be cFXG and eAF OR cFX and eGAF

hope i make myself clear...