Suggestion: Use reed-solomon encoding to reduce data size

[A]

The current implementation of the program appears to copy the encrypted file into each horcrux, which becomes pretty storage intensive with a larger file and more horcruxes.

n is the number of horcruxes, t the number needed to ressurect, s is size of the file, t ≤ n
Reed-solomon encoding can split the original file into n pieces, each piece has a size of s/t. Any combination of t pieces can be used to recreate the original file.

So the total space used by the horcruxes would be n*(s/t) instead of n*s.

This should also ensure the integrity of the data as the reconstruction of the file should fail if a piece is modified.