Expanse an AES-128 key to 16 round keys

expanse_aes_key.py

# Expanse an AES-128 key to 16 round keys

import sys

# AES S-Box
s_box = [
    0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
    0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
    0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
    0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
    0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
    0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
    0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
    0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
    0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
    0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
    0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
    0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
    0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
    0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
    0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
    0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16,
]

# AES Rcon
r_con = [
    [0x00, 0x00, 0x00, 0x00],
    [0x01, 0x00, 0x00, 0x00],
    [0x02, 0x00, 0x00, 0x00],
    [0x04, 0x00, 0x00, 0x00],
    [0x08, 0x00, 0x00, 0x00],
    [0x10, 0x00, 0x00, 0x00],
    [0x20, 0x00, 0x00, 0x00],
    [0x40, 0x00, 0x00, 0x00],
    [0x80, 0x00, 0x00, 0x00],
    [0x1b, 0x00, 0x00, 0x00],
    [0x36, 0x00, 0x00, 0x00],
]

def sub_word(word):
    return [s_box[b] for b in word]

def rot_word(word):
    return word[1:] + word[:1]

def key_expansion(key):
    expanded_key = key.copy()
    nk = len(key) // 4
    rcon_idx = 1

    while len(expanded_key) < 176:
        temp = expanded_key[-4:]

        if len(expanded_key) % 16 == 0:
            temp = sub_word(rot_word(temp))
            temp[0] ^= r_con[rcon_idx][0]
            rcon_idx += 1

        for i in range(4):
            temp[i] ^= expanded_key[-16 + i]

        expanded_key.extend(temp)

    return expanded_key

def main():
    key = input("Enter the AES-128 key (16 bytes in hexadecimal): ")
    key = [int(key[i:i+2], 16) for i in range(0, len(key), 2)]

    if len(key) != 16:
        print("Invalid key length. Please enter 16 bytes in hexadecimal.")
        sys.exit(1)

    round_keys = key_expansion(key)

    print("\nRound Keys:")
    for i in range(len(round_keys) // 16):
        round_key = round_keys[i * 16 : (i + 1) * 16]
        print(f"Round {i+1}: {' '.join([f'{b:02X}' for b in round_key])}")

if __name__ == "__main__":
    main()