Hello all! Based on the feedback I've received in the last day I've made some improvements:

I'm now making use of Samir's Secret Sharing Scheme meaning you can now specify a threshold of horcruxes required to resurrect the original file (hopefully putting me in better standing among the HP crowd)

If your threshold equals the total number of horcruxes, I'll divide the content evenly between each horcrux to reduce file size. Otherwise each horcrux will contain the same encrypted content

As I've mentioned in another comment I no longer load files into memory so the program runs pretty fast

Thanks for the valuable feedback everyone!