Endiannes & Splitting Values

[BitGuy via Digitalmars-d-learn]

I'm trying to implement a feistel cipher that'll give the same 
results regardless of the endianness of the machine it runs on. 
To make the cipher I need to split a 64bit value into two 32bit 
values, mess with them, and then put them back together. I can 
think of a few ways to split a 64bit value with versions or the 
endianness functions in bitmanip but it all seems pretty messy 
for just wanting to split a value... I'm thinking maybe I can 
just cast and bitshift so I can forget about the endianness but 
I'm not really sure about the casting down rules and if that'd 
work?