To run the algorithm simply use:
python3 main.py --keysize $KEYSIZE --keyfile $KEYFILE --inputfile $INPUTFILE --outputfile$OUTFILENAME --mode $MODE
main.py takes arguments shown above.
--keysize can vary between 128 and 256 and defines the key length (Nk), which can be 4 or 8 bytes respectively.
Nb, the block width, does not change.
Nr, the number of rounds, is either 10 or 14 respectively.
Based of whether the mode is encrypt or decrypt, the cipher or inv_cipher functions are called.
If encrypting then the input file is also padded.
This file contains a lot of array's that are supposed to make multiplication in GF(2^8) possible.
sub_bytes and its inverse counterpart just plug into the sbox array.
transpose was written because at one point I confused row and column order
and didn't have enough time ot rewrite the math.
shift_rows and the inverse counterpart shift the 0th row by 0, the 1st by 1, and so on -
all in their respective direction.
mix_columns and its inverse counterpart do matrix multiply with some constants.
To make multiplication possible I used the constant array at the head of the file.
add_round_key adds the word generated in KeyExpansion
for the respective round.
rot_word just rotates the bytes in a word
, and sub_word substitutes each byte using the sbox.
key_expansion sandwhiches bytes from the byte array input and does what it does.
Most of which just involves XOR and plugging into sub_word, rot_word, and rcon
cipher and inv_cipher implement all the functions in the correct order as specified by NIST.