aes.py

"""
usage: {0} <mode> [<options>]

modes:
  genkey SIZE > KEYFILE
  encrypt KEYFILE < FILE > ENC_FILE
  decrypt KEYFILE < ENC_FILE > FILE

examples:
  # encrypt a file
  python {0} encrypt key.txt < file.txt > file.txt.enc

  # decrypt a file
  python {0} decrypt key.txt < file.txt.enc
"""
# see https://en.wikipedia.org/wiki/Advanced_Encryption_Standard
#     https://nvlpubs.nist.gov/nistpubs/fips/nist.fips.197.pdf
#     https://nvlpubs.nist.gov/nistpubs/legacy/sp/nistspecialpublication800-38a.pdf

from random import getrandbits
from io import SEEK_CUR
from enum import Enum

# Types of AES keys
# (see https://en.wikipedia.org/wiki/Advanced_Encryption_Standard,
#  https://en.wikipedia.org/wiki/Rijndael_key_schedule)
KEY_TYPES = {
    "128": {"size": 128, "rounds": 10, "key_n_size": 16, "expkey_size": 176},
    "192": {"size": 192, "rounds": 12, "key_n_size": 24, "expkey_size": 208},
    "256": {"size": 256, "rounds": 14, "key_n_size": 32, "expkey_size": 240},
}

# AES block dim
NB = 4

# Rijndael S-Box lookup tables
# (see https://en.wikipedia.org/wiki/Rijndael_S-box)
SBOX = (
    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
)
SBOX_INV = (
    0x52, 0x09, 0x6A, 0xD5, 0x30, 0x36, 0xA5, 0x38, 0xBF, 0x40, 0xA3, 0x9E,
    0x81, 0xF3, 0xD7, 0xFB, 0x7C, 0xE3, 0x39, 0x82, 0x9B, 0x2F, 0xFF, 0x87,
    0x34, 0x8E, 0x43, 0x44, 0xC4, 0xDE, 0xE9, 0xCB, 0x54, 0x7B, 0x94, 0x32,
    0xA6, 0xC2, 0x23, 0x3D, 0xEE, 0x4C, 0x95, 0x0B, 0x42, 0xFA, 0xC3, 0x4E,
    0x08, 0x2E, 0xA1, 0x66, 0x28, 0xD9, 0x24, 0xB2, 0x76, 0x5B, 0xA2, 0x49,
    0x6D, 0x8B, 0xD1, 0x25, 0x72, 0xF8, 0xF6, 0x64, 0x86, 0x68, 0x98, 0x16,
    0xD4, 0xA4, 0x5C, 0xCC, 0x5D, 0x65, 0xB6, 0x92, 0x6C, 0x70, 0x48, 0x50,
    0xFD, 0xED, 0xB9, 0xDA, 0x5E, 0x15, 0x46, 0x57, 0xA7, 0x8D, 0x9D, 0x84,
    0x90, 0xD8, 0xAB, 0x00, 0x8C, 0xBC, 0xD3, 0x0A, 0xF7, 0xE4, 0x58, 0x05,
    0xB8, 0xB3, 0x45, 0x06, 0xD0, 0x2C, 0x1E, 0x8F, 0xCA, 0x3F, 0x0F, 0x02,
    0xC1, 0xAF, 0xBD, 0x03, 0x01, 0x13, 0x8A, 0x6B, 0x3A, 0x91, 0x11, 0x41,
    0x4F, 0x67, 0xDC, 0xEA, 0x97, 0xF2, 0xCF, 0xCE, 0xF0, 0xB4, 0xE6, 0x73,
    0x96, 0xAC, 0x74, 0x22, 0xE7, 0xAD, 0x35, 0x85, 0xE2, 0xF9, 0x37, 0xE8,
    0x1C, 0x75, 0xDF, 0x6E, 0x47, 0xF1, 0x1A, 0x71, 0x1D, 0x29, 0xC5, 0x89,
    0x6F, 0xB7, 0x62, 0x0E, 0xAA, 0x18, 0xBE, 0x1B, 0xFC, 0x56, 0x3E, 0x4B,
    0xC6, 0xD2, 0x79, 0x20, 0x9A, 0xDB, 0xC0, 0xFE, 0x78, 0xCD, 0x5A, 0xF4,
    0x1F, 0xDD, 0xA8, 0x33, 0x88, 0x07, 0xC7, 0x31, 0xB1, 0x12, 0x10, 0x59,
    0x27, 0x80, 0xEC, 0x5F, 0x60, 0x51, 0x7F, 0xA9, 0x19, 0xB5, 0x4A, 0x0D,
    0x2D, 0xE5, 0x7A, 0x9F, 0x93, 0xC9, 0x9C, 0xEF, 0xA0, 0xE0, 0x3B, 0x4D,
    0xAE, 0x2A, 0xF5, 0xB0, 0xC8, 0xEB, 0xBB, 0x3C, 0x83, 0x53, 0x99, 0x61,
    0x17, 0x2B, 0x04, 0x7E, 0xBA, 0x77, 0xD6, 0x26, 0xE1, 0x69, 0x14, 0x63,
    0x55, 0x21, 0x0C, 0x7D
)

# Rijndael Rcon values up to the 11th (used for AES-256)
# (see https://en.wikipedia.org/wiki/Rijndael_key_schedule#Rcon)
RCON = (0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36)

# Galois field (2**8) multiplication lookup tables
# (see https://en.wikipedia.org/wiki/Rijndael_MixColumns)
GF256MUL = {
    2: (
        0x00, 0x02, 0x04, 0x06, 0x08, 0x0a, 0x0c, 0x0e, 0x10, 0x12, 0x14, 0x16,
        0x18, 0x1a, 0x1c, 0x1e, 0x20, 0x22, 0x24, 0x26, 0x28, 0x2a, 0x2c, 0x2e,
        0x30, 0x32, 0x34, 0x36, 0x38, 0x3a, 0x3c, 0x3e, 0x40, 0x42, 0x44, 0x46,
        0x48, 0x4a, 0x4c, 0x4e, 0x50, 0x52, 0x54, 0x56, 0x58, 0x5a, 0x5c, 0x5e,
        0x60, 0x62, 0x64, 0x66, 0x68, 0x6a, 0x6c, 0x6e, 0x70, 0x72, 0x74, 0x76,
        0x78, 0x7a, 0x7c, 0x7e, 0x80, 0x82, 0x84, 0x86, 0x88, 0x8a, 0x8c, 0x8e,
        0x90, 0x92, 0x94, 0x96, 0x98, 0x9a, 0x9c, 0x9e, 0xa0, 0xa2, 0xa4, 0xa6,
        0xa8, 0xaa, 0xac, 0xae, 0xb0, 0xb2, 0xb4, 0xb6, 0xb8, 0xba, 0xbc, 0xbe,
        0xc0, 0xc2, 0xc4, 0xc6, 0xc8, 0xca, 0xcc, 0xce, 0xd0, 0xd2, 0xd4, 0xd6,
        0xd8, 0xda, 0xdc, 0xde, 0xe0, 0xe2, 0xe4, 0xe6, 0xe8, 0xea, 0xec, 0xee,
        0xf0, 0xf2, 0xf4, 0xf6, 0xf8, 0xfa, 0xfc, 0xfe, 0x1b, 0x19, 0x1f, 0x1d,
        0x13, 0x11, 0x17, 0x15, 0x0b, 0x09, 0x0f, 0x0d, 0x03, 0x01, 0x07, 0x05,
        0x3b, 0x39, 0x3f, 0x3d, 0x33, 0x31, 0x37, 0x35, 0x2b, 0x29, 0x2f, 0x2d,
        0x23, 0x21, 0x27, 0x25, 0x5b, 0x59, 0x5f, 0x5d, 0x53, 0x51, 0x57, 0x55,
        0x4b, 0x49, 0x4f, 0x4d, 0x43, 0x41, 0x47, 0x45, 0x7b, 0x79, 0x7f, 0x7d,
        0x73, 0x71, 0x77, 0x75, 0x6b, 0x69, 0x6f, 0x6d, 0x63, 0x61, 0x67, 0x65,
        0x9b, 0x99, 0x9f, 0x9d, 0x93, 0x91, 0x97, 0x95, 0x8b, 0x89, 0x8f, 0x8d,
        0x83, 0x81, 0x87, 0x85, 0xbb, 0xb9, 0xbf, 0xbd, 0xb3, 0xb1, 0xb7, 0xb5,
        0xab, 0xa9, 0xaf, 0xad, 0xa3, 0xa1, 0xa7, 0xa5, 0xdb, 0xd9, 0xdf, 0xdd,
        0xd3, 0xd1, 0xd7, 0xd5, 0xcb, 0xc9, 0xcf, 0xcd, 0xc3, 0xc1, 0xc7, 0xc5,
        0xfb, 0xf9, 0xff, 0xfd, 0xf3, 0xf1, 0xf7, 0xf5, 0xeb, 0xe9, 0xef, 0xed,
        0xe3, 0xe1, 0xe7, 0xe5
    ),
    3: (
        0x00, 0x03, 0x06, 0x05, 0x0c, 0x0f, 0x0a, 0x09, 0x18, 0x1b, 0x1e, 0x1d,
        0x14, 0x17, 0x12, 0x11, 0x30, 0x33, 0x36, 0x35, 0x3c, 0x3f, 0x3a, 0x39,
        0x28, 0x2b, 0x2e, 0x2d, 0x24, 0x27, 0x22, 0x21, 0x60, 0x63, 0x66, 0x65,
        0x6c, 0x6f, 0x6a, 0x69, 0x78, 0x7b, 0x7e, 0x7d, 0x74, 0x77, 0x72, 0x71,
        0x50, 0x53, 0x56, 0x55, 0x5c, 0x5f, 0x5a, 0x59, 0x48, 0x4b, 0x4e, 0x4d,
        0x44, 0x47, 0x42, 0x41, 0xc0, 0xc3, 0xc6, 0xc5, 0xcc, 0xcf, 0xca, 0xc9,
        0xd8, 0xdb, 0xde, 0xdd, 0xd4, 0xd7, 0xd2, 0xd1, 0xf0, 0xf3, 0xf6, 0xf5,
        0xfc, 0xff, 0xfa, 0xf9, 0xe8, 0xeb, 0xee, 0xed, 0xe4, 0xe7, 0xe2, 0xe1,
        0xa0, 0xa3, 0xa6, 0xa5, 0xac, 0xaf, 0xaa, 0xa9, 0xb8, 0xbb, 0xbe, 0xbd,
        0xb4, 0xb7, 0xb2, 0xb1, 0x90, 0x93, 0x96, 0x95, 0x9c, 0x9f, 0x9a, 0x99,
        0x88, 0x8b, 0x8e, 0x8d, 0x84, 0x87, 0x82, 0x81, 0x9b, 0x98, 0x9d, 0x9e,
        0x97, 0x94, 0x91, 0x92, 0x83, 0x80, 0x85, 0x86, 0x8f, 0x8c, 0x89, 0x8a,
        0xab, 0xa8, 0xad, 0xae, 0xa7, 0xa4, 0xa1, 0xa2, 0xb3, 0xb0, 0xb5, 0xb6,
        0xbf, 0xbc, 0xb9, 0xba, 0xfb, 0xf8, 0xfd, 0xfe, 0xf7, 0xf4, 0xf1, 0xf2,
        0xe3, 0xe0, 0xe5, 0xe6, 0xef, 0xec, 0xe9, 0xea, 0xcb, 0xc8, 0xcd, 0xce,
        0xc7, 0xc4, 0xc1, 0xc2, 0xd3, 0xd0, 0xd5, 0xd6, 0xdf, 0xdc, 0xd9, 0xda,
        0x5b, 0x58, 0x5d, 0x5e, 0x57, 0x54, 0x51, 0x52, 0x43, 0x40, 0x45, 0x46,
        0x4f, 0x4c, 0x49, 0x4a, 0x6b, 0x68, 0x6d, 0x6e, 0x67, 0x64, 0x61, 0x62,
        0x73, 0x70, 0x75, 0x76, 0x7f, 0x7c, 0x79, 0x7a, 0x3b, 0x38, 0x3d, 0x3e,
        0x37, 0x34, 0x31, 0x32, 0x23, 0x20, 0x25, 0x26, 0x2f, 0x2c, 0x29, 0x2a,
        0x0b, 0x08, 0x0d, 0x0e, 0x07, 0x04, 0x01, 0x02, 0x13, 0x10, 0x15, 0x16,
        0x1f, 0x1c, 0x19, 0x1a
    ),
    9: (
        0x00, 0x09, 0x12, 0x1b, 0x24, 0x2d, 0x36, 0x3f, 0x48, 0x41, 0x5a, 0x53,
        0x6c, 0x65, 0x7e, 0x77, 0x90, 0x99, 0x82, 0x8b, 0xb4, 0xbd, 0xa6, 0xaf,
        0xd8, 0xd1, 0xca, 0xc3, 0xfc, 0xf5, 0xee, 0xe7, 0x3b, 0x32, 0x29, 0x20,
        0x1f, 0x16, 0x0d, 0x04, 0x73, 0x7a, 0x61, 0x68, 0x57, 0x5e, 0x45, 0x4c,
        0xab, 0xa2, 0xb9, 0xb0, 0x8f, 0x86, 0x9d, 0x94, 0xe3, 0xea, 0xf1, 0xf8,
        0xc7, 0xce, 0xd5, 0xdc, 0x76, 0x7f, 0x64, 0x6d, 0x52, 0x5b, 0x40, 0x49,
        0x3e, 0x37, 0x2c, 0x25, 0x1a, 0x13, 0x08, 0x01, 0xe6, 0xef, 0xf4, 0xfd,
        0xc2, 0xcb, 0xd0, 0xd9, 0xae, 0xa7, 0xbc, 0xb5, 0x8a, 0x83, 0x98, 0x91,
        0x4d, 0x44, 0x5f, 0x56, 0x69, 0x60, 0x7b, 0x72, 0x05, 0x0c, 0x17, 0x1e,
        0x21, 0x28, 0x33, 0x3a, 0xdd, 0xd4, 0xcf, 0xc6, 0xf9, 0xf0, 0xeb, 0xe2,
        0x95, 0x9c, 0x87, 0x8e, 0xb1, 0xb8, 0xa3, 0xaa, 0xec, 0xe5, 0xfe, 0xf7,
        0xc8, 0xc1, 0xda, 0xd3, 0xa4, 0xad, 0xb6, 0xbf, 0x80, 0x89, 0x92, 0x9b,
        0x7c, 0x75, 0x6e, 0x67, 0x58, 0x51, 0x4a, 0x43, 0x34, 0x3d, 0x26, 0x2f,
        0x10, 0x19, 0x02, 0x0b, 0xd7, 0xde, 0xc5, 0xcc, 0xf3, 0xfa, 0xe1, 0xe8,
        0x9f, 0x96, 0x8d, 0x84, 0xbb, 0xb2, 0xa9, 0xa0, 0x47, 0x4e, 0x55, 0x5c,
        0x63, 0x6a, 0x71, 0x78, 0x0f, 0x06, 0x1d, 0x14, 0x2b, 0x22, 0x39, 0x30,
        0x9a, 0x93, 0x88, 0x81, 0xbe, 0xb7, 0xac, 0xa5, 0xd2, 0xdb, 0xc0, 0xc9,
        0xf6, 0xff, 0xe4, 0xed, 0x0a, 0x03, 0x18, 0x11, 0x2e, 0x27, 0x3c, 0x35,
        0x42, 0x4b, 0x50, 0x59, 0x66, 0x6f, 0x74, 0x7d, 0xa1, 0xa8, 0xb3, 0xba,
        0x85, 0x8c, 0x97, 0x9e, 0xe9, 0xe0, 0xfb, 0xf2, 0xcd, 0xc4, 0xdf, 0xd6,
        0x31, 0x38, 0x23, 0x2a, 0x15, 0x1c, 0x07, 0x0e, 0x79, 0x70, 0x6b, 0x62,
        0x5d, 0x54, 0x4f, 0x46
    ),
    11: (
        0x00, 0x0b, 0x16, 0x1d, 0x2c, 0x27, 0x3a, 0x31, 0x58, 0x53, 0x4e, 0x45,
        0x74, 0x7f, 0x62, 0x69, 0xb0, 0xbb, 0xa6, 0xad, 0x9c, 0x97, 0x8a, 0x81,
        0xe8, 0xe3, 0xfe, 0xf5, 0xc4, 0xcf, 0xd2, 0xd9, 0x7b, 0x70, 0x6d, 0x66,
        0x57, 0x5c, 0x41, 0x4a, 0x23, 0x28, 0x35, 0x3e, 0x0f, 0x04, 0x19, 0x12,
        0xcb, 0xc0, 0xdd, 0xd6, 0xe7, 0xec, 0xf1, 0xfa, 0x93, 0x98, 0x85, 0x8e,
        0xbf, 0xb4, 0xa9, 0xa2, 0xf6, 0xfd, 0xe0, 0xeb, 0xda, 0xd1, 0xcc, 0xc7,
        0xae, 0xa5, 0xb8, 0xb3, 0x82, 0x89, 0x94, 0x9f, 0x46, 0x4d, 0x50, 0x5b,
        0x6a, 0x61, 0x7c, 0x77, 0x1e, 0x15, 0x08, 0x03, 0x32, 0x39, 0x24, 0x2f,
        0x8d, 0x86, 0x9b, 0x90, 0xa1, 0xaa, 0xb7, 0xbc, 0xd5, 0xde, 0xc3, 0xc8,
        0xf9, 0xf2, 0xef, 0xe4, 0x3d, 0x36, 0x2b, 0x20, 0x11, 0x1a, 0x07, 0x0c,
        0x65, 0x6e, 0x73, 0x78, 0x49, 0x42, 0x5f, 0x54, 0xf7, 0xfc, 0xe1, 0xea,
        0xdb, 0xd0, 0xcd, 0xc6, 0xaf, 0xa4, 0xb9, 0xb2, 0x83, 0x88, 0x95, 0x9e,
        0x47, 0x4c, 0x51, 0x5a, 0x6b, 0x60, 0x7d, 0x76, 0x1f, 0x14, 0x09, 0x02,
        0x33, 0x38, 0x25, 0x2e, 0x8c, 0x87, 0x9a, 0x91, 0xa0, 0xab, 0xb6, 0xbd,
        0xd4, 0xdf, 0xc2, 0xc9, 0xf8, 0xf3, 0xee, 0xe5, 0x3c, 0x37, 0x2a, 0x21,
        0x10, 0x1b, 0x06, 0x0d, 0x64, 0x6f, 0x72, 0x79, 0x48, 0x43, 0x5e, 0x55,
        0x01, 0x0a, 0x17, 0x1c, 0x2d, 0x26, 0x3b, 0x30, 0x59, 0x52, 0x4f, 0x44,
        0x75, 0x7e, 0x63, 0x68, 0xb1, 0xba, 0xa7, 0xac, 0x9d, 0x96, 0x8b, 0x80,
        0xe9, 0xe2, 0xff, 0xf4, 0xc5, 0xce, 0xd3, 0xd8, 0x7a, 0x71, 0x6c, 0x67,
        0x56, 0x5d, 0x40, 0x4b, 0x22, 0x29, 0x34, 0x3f, 0x0e, 0x05, 0x18, 0x13,
        0xca, 0xc1, 0xdc, 0xd7, 0xe6, 0xed, 0xf0, 0xfb, 0x92, 0x99, 0x84, 0x8f,
        0xbe, 0xb5, 0xa8, 0xa3
    ),
    13: (
        0x00, 0x0d, 0x1a, 0x17, 0x34, 0x39, 0x2e, 0x23, 0x68, 0x65, 0x72, 0x7f,
        0x5c, 0x51, 0x46, 0x4b, 0xd0, 0xdd, 0xca, 0xc7, 0xe4, 0xe9, 0xfe, 0xf3,
        0xb8, 0xb5, 0xa2, 0xaf, 0x8c, 0x81, 0x96, 0x9b, 0xbb, 0xb6, 0xa1, 0xac,
        0x8f, 0x82, 0x95, 0x98, 0xd3, 0xde, 0xc9, 0xc4, 0xe7, 0xea, 0xfd, 0xf0,
        0x6b, 0x66, 0x71, 0x7c, 0x5f, 0x52, 0x45, 0x48, 0x03, 0x0e, 0x19, 0x14,
        0x37, 0x3a, 0x2d, 0x20, 0x6d, 0x60, 0x77, 0x7a, 0x59, 0x54, 0x43, 0x4e,
        0x05, 0x08, 0x1f, 0x12, 0x31, 0x3c, 0x2b, 0x26, 0xbd, 0xb0, 0xa7, 0xaa,
        0x89, 0x84, 0x93, 0x9e, 0xd5, 0xd8, 0xcf, 0xc2, 0xe1, 0xec, 0xfb, 0xf6,
        0xd6, 0xdb, 0xcc, 0xc1, 0xe2, 0xef, 0xf8, 0xf5, 0xbe, 0xb3, 0xa4, 0xa9,
        0x8a, 0x87, 0x90, 0x9d, 0x06, 0x0b, 0x1c, 0x11, 0x32, 0x3f, 0x28, 0x25,
        0x6e, 0x63, 0x74, 0x79, 0x5a, 0x57, 0x40, 0x4d, 0xda, 0xd7, 0xc0, 0xcd,
        0xee, 0xe3, 0xf4, 0xf9, 0xb2, 0xbf, 0xa8, 0xa5, 0x86, 0x8b, 0x9c, 0x91,
        0x0a, 0x07, 0x10, 0x1d, 0x3e, 0x33, 0x24, 0x29, 0x62, 0x6f, 0x78, 0x75,
        0x56, 0x5b, 0x4c, 0x41, 0x61, 0x6c, 0x7b, 0x76, 0x55, 0x58, 0x4f, 0x42,
        0x09, 0x04, 0x13, 0x1e, 0x3d, 0x30, 0x27, 0x2a, 0xb1, 0xbc, 0xab, 0xa6,
        0x85, 0x88, 0x9f, 0x92, 0xd9, 0xd4, 0xc3, 0xce, 0xed, 0xe0, 0xf7, 0xfa,
        0xb7, 0xba, 0xad, 0xa0, 0x83, 0x8e, 0x99, 0x94, 0xdf, 0xd2, 0xc5, 0xc8,
        0xeb, 0xe6, 0xf1, 0xfc, 0x67, 0x6a, 0x7d, 0x70, 0x53, 0x5e, 0x49, 0x44,
        0x0f, 0x02, 0x15, 0x18, 0x3b, 0x36, 0x21, 0x2c, 0x0c, 0x01, 0x16, 0x1b,
        0x38, 0x35, 0x22, 0x2f, 0x64, 0x69, 0x7e, 0x73, 0x50, 0x5d, 0x4a, 0x47,
        0xdc, 0xd1, 0xc6, 0xcb, 0xe8, 0xe5, 0xf2, 0xff, 0xb4, 0xb9, 0xae, 0xa3,
        0x80, 0x8d, 0x9a, 0x97
    ),
    14: (
       0x00, 0x0e, 0x1c, 0x12, 0x38, 0x36, 0x24, 0x2a, 0x70, 0x7e, 0x6c, 0x62,
       0x48, 0x46, 0x54, 0x5a, 0xe0, 0xee, 0xfc, 0xf2, 0xd8, 0xd6, 0xc4, 0xca,
       0x90, 0x9e, 0x8c, 0x82, 0xa8, 0xa6, 0xb4, 0xba, 0xdb, 0xd5, 0xc7, 0xc9,
       0xe3, 0xed, 0xff, 0xf1, 0xab, 0xa5, 0xb7, 0xb9, 0x93, 0x9d, 0x8f, 0x81,
       0x3b, 0x35, 0x27, 0x29, 0x03, 0x0d, 0x1f, 0x11, 0x4b, 0x45, 0x57, 0x59,
       0x73, 0x7d, 0x6f, 0x61, 0xad, 0xa3, 0xb1, 0xbf, 0x95, 0x9b, 0x89, 0x87,
       0xdd, 0xd3, 0xc1, 0xcf, 0xe5, 0xeb, 0xf9, 0xf7, 0x4d, 0x43, 0x51, 0x5f,
       0x75, 0x7b, 0x69, 0x67, 0x3d, 0x33, 0x21, 0x2f, 0x05, 0x0b, 0x19, 0x17,
       0x76, 0x78, 0x6a, 0x64, 0x4e, 0x40, 0x52, 0x5c, 0x06, 0x08, 0x1a, 0x14,
       0x3e, 0x30, 0x22, 0x2c, 0x96, 0x98, 0x8a, 0x84, 0xae, 0xa0, 0xb2, 0xbc,
       0xe6, 0xe8, 0xfa, 0xf4, 0xde, 0xd0, 0xc2, 0xcc, 0x41, 0x4f, 0x5d, 0x53,
       0x79, 0x77, 0x65, 0x6b, 0x31, 0x3f, 0x2d, 0x23, 0x09, 0x07, 0x15, 0x1b,
       0xa1, 0xaf, 0xbd, 0xb3, 0x99, 0x97, 0x85, 0x8b, 0xd1, 0xdf, 0xcd, 0xc3,
       0xe9, 0xe7, 0xf5, 0xfb, 0x9a, 0x94, 0x86, 0x88, 0xa2, 0xac, 0xbe, 0xb0,
       0xea, 0xe4, 0xf6, 0xf8, 0xd2, 0xdc, 0xce, 0xc0, 0x7a, 0x74, 0x66, 0x68,
       0x42, 0x4c, 0x5e, 0x50, 0x0a, 0x04, 0x16, 0x18, 0x32, 0x3c, 0x2e, 0x20,
       0xec, 0xe2, 0xf0, 0xfe, 0xd4, 0xda, 0xc8, 0xc6, 0x9c, 0x92, 0x80, 0x8e,
       0xa4, 0xaa, 0xb8, 0xb6, 0x0c, 0x02, 0x10, 0x1e, 0x34, 0x3a, 0x28, 0x26,
       0x7c, 0x72, 0x60, 0x6e, 0x44, 0x4a, 0x58, 0x56, 0x37, 0x39, 0x2b, 0x25,
       0x0f, 0x01, 0x13, 0x1d, 0x47, 0x49, 0x5b, 0x55, 0x7f, 0x71, 0x63, 0x6d,
       0xd7, 0xd9, 0xcb, 0xc5, 0xef, 0xe1, 0xf3, 0xfd, 0xa7, 0xa9, 0xbb, 0xb5,
       0x9f, 0x91, 0x83, 0x8d
    ),
}


class MoO(Enum):
    '''
    Block cipher mode of operation

    (see https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation)
    '''
    ECB = 0
    CBC = 1
    # TODO: add support for other modes
    # PCBC = 2
    # CFB = 3
    # OFB = 4
    # CTR = 5


def _bytes2block(bs, dim=NB):
    '''
    Bytes to block (column-major order matrix of bytes) utility function
    (see https://en.wikipedia.org/wiki/Advanced_Encryption_Standard#Description_of_the_cipher)
    '''
    # array of rows
    block = [[None for _ in range(dim)] for _ in range(dim)]
    for i in range(dim * dim):
        block[i % dim][i // dim] = bs[i]
    return block


def _block2bytes(block, dim=NB):
    '''
    Block (column-major order matrix of bytes) to bytes utility function
    (see https://en.wikipedia.org/wiki/Advanced_Encryption_Standard#Description_of_the_cipher)
    '''
    bs = []
    for i in range(dim * dim):
        bs.append(block[i % dim][i // dim])
    return bytes(bs)


def _rot_word(word):
    w = word[1:] + word[:1]
    word.clear()
    word.extend(w)


def _sub_word(word):
    for i in range(len(word)):
        word[i] = SBOX[word[i]]


def _key_expansion(key, keycfg):
    '''
    Rijndael key schedule
    (see https://en.wikipedia.org/wiki/Rijndael_key_schedule)
    '''
    expkeysize = keycfg["expkey_size"]
    key = [b for b in key]
    expkey = [0] * expkeysize

    nk = keycfg["key_n_size"]
    cursize = nk
    expkey[0:cursize] = key[0:cursize]

    while cursize < expkeysize:
        temp = expkey[cursize-4:cursize]
        if cursize % nk == 0:
            _rot_word(temp)
            _sub_word(temp)
            temp[0] ^= RCON[cursize // nk]
        if (keycfg["size"] == 256) and (cursize % nk) == 16:
            _sub_word(temp)

        for i in range(len(temp)):
            expkey[cursize] = expkey[cursize - nk] ^ temp[i]
            cursize += 1

    return bytes(expkey)


def _add_round_key(block, rkey):
    '''
    AES' AddRoundKey step
    (see https://en.wikipedia.org/wiki/Advanced_Encryption_Standard#The_AddRoundKey_step)
    '''
    for i in range(NB*NB):
        block[i % NB][i // NB] ^= rkey[i]


def _sub_bytes(block):
    '''
    AES' SubBytes step
    (see https://en.wikipedia.org/wiki/Advanced_Encryption_Standard#The_SubBytes_step,
         https://en.wikipedia.org/wiki/Rijndael_S-box)
    '''
    for i in range(NB):
        for j in range(NB):
            block[i][j] = SBOX[block[i][j]]


def _sub_bytes_inv(block):
    '''
    AES' inverse SubBytes step
    (see https://en.wikipedia.org/wiki/Advanced_Encryption_Standard#The_SubBytes_step,
         https://en.wikipedia.org/wiki/Rijndael_S-box)
    '''
    for i in range(NB):
        for j in range(NB):
            block[i][j] = SBOX_INV[block[i][j]]


def _shift_rows(block):
    '''
    AES' ShiftRows step
    (see https://en.wikipedia.org/wiki/Advanced_Encryption_Standard#The_ShiftRows_step)
    '''
    block[1] = block[1][1:] + block[1][:1]
    block[2] = block[2][2:] + block[2][:2]
    block[3] = block[3][3:] + block[3][:3]


def _shift_rows_inv(block):
    '''
    AES' inverse ShiftRows step
    (see https://en.wikipedia.org/wiki/Advanced_Encryption_Standard#The_ShiftRows_step)
    '''
    block[1] = block[1][3:] + block[1][:3]
    block[2] = block[2][2:] + block[2][:2]
    block[3] = block[3][1:] + block[3][:1]


def _mix_columns(block):
    '''
    AES' MixColumns step
    (see https://en.wikipedia.org/wiki/Rijndael_MixColumns)
    '''
    for i in range(len(block)):
        i0 = block[0][i]
        i1 = block[1][i]
        i2 = block[2][i]
        i3 = block[3][i]
        block[0][i] = GF256MUL[2][i0] ^ GF256MUL[3][i1] ^ i2 ^ i3
        block[1][i] = i0 ^ GF256MUL[2][i1] ^ GF256MUL[3][i2] ^ i3
        block[2][i] = i0 ^ i1 ^ GF256MUL[2][i2] ^ GF256MUL[3][i3]
        block[3][i] = GF256MUL[3][i0] ^ i1 ^ i2 ^ GF256MUL[2][i3]


def _mix_columns_inv(block):
    '''
    AES' inverse MixColumns step
    (see https://en.wikipedia.org/wiki/Rijndael_MixColumns)
    '''
    for i in range(len(block)):
        i0 = block[0][i]
        i1 = block[1][i]
        i2 = block[2][i]
        i3 = block[3][i]
        block[0][i] = GF256MUL[14][i0] ^ GF256MUL[11][i1] \
            ^ GF256MUL[13][i2] ^ GF256MUL[9][i3]
        block[1][i] = GF256MUL[9][i0] ^ GF256MUL[14][i1] \
            ^ GF256MUL[11][i2] ^ GF256MUL[13][i3]
        block[2][i] = GF256MUL[13][i0] ^ GF256MUL[9][i1] \
            ^ GF256MUL[14][i2] ^ GF256MUL[11][i3]
        block[3][i] = GF256MUL[11][i0] ^ GF256MUL[13][i1] \
            ^ GF256MUL[9][i2] ^ GF256MUL[14][i3]


def _encrypt_moo(readable, writable, moo, iv=None):
    '''
    Block cipher mode of operation
    (see https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation)
    '''
    if moo not in MoO:
        raise ValueError

    if moo != MoO.ECB:
        if not iv:
            iv = getrandbits(16 * 8).to_bytes(16, 'little', signed=False)
        writable.write(bytes(iv))

    llen = None
    for pt in iter(lambda: readable.read(NB*NB), b""):
        llen = len(pt)

        if llen < NB*NB:
            # PKCS#7 padding
            # (see https://en.wikipedia.org/wiki/Padding_(cryptography)#PKCS7)
            if (moo == MoO.ECB) or (moo == MoO.CBC):
                pn = (NB*NB) - llen
                pt += bytes([pn for _ in range(pn)])

        if moo == MoO.CBC:
            pt = [b for b in pt]
            for i in range(NB*NB):
                pt[i] ^= iv[i]
            pt = bytes(pt)

        # block is modified in place
        block = _bytes2block(pt)
        yield block
        bs = _block2bytes(block)

        if moo == MoO.CBC:
            iv = [b for b in bs]

        writable.write(bs)

    if llen == NB*NB:
        # PKCS#7 padding
        # (see https://en.wikipedia.org/wiki/Padding_(cryptography)#PKCS7)
        if (moo == MoO.ECB) or (moo == MoO.CBC):
            block = _bytes2block(bytes([llen for _ in range(llen)]))
            yield block
            writable.write(_block2bytes(block))


def _decrypt_moo(readable, writable, moo):
    '''
    Block cipher mode of operation
    (see https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation)
    '''
    if moo not in MoO:
        raise ValueError

    if moo != MoO.ECB:
        iv = [b for b in readable.read(NB*NB)]

    for ct in iter(lambda: readable.read(NB*NB), b""):
        # FIXME: ugly hack
        last_block = (readable.read(1) == b"")
        if not last_block:
            readable.seek(-1, SEEK_CUR)

        if len(ct) < NB*NB:
            if (moo == MoO.ECB) or (moo == MoO.CBC):
                raise ValueError

        block = _bytes2block(ct)
        # block is modified in place
        yield block
        bs = _block2bytes(block)

        if (moo == MoO.CBC) and (not last_block):
            bs = [b for b in bs]
            for i in range(NB*NB):
                bs[i] ^= iv[i]
            iv = ct

        # PKCS#7 padding
        # (see https://en.wikipedia.org/wiki/Padding_(cryptography)#PKCS7)
        if ((moo == MoO.ECB) or (moo == MoO.CBC)) and last_block:
            bs = bytes(bs[:-int(bs[-1])])
        else:
            bs = bytes(bs)

        writable.write(bs)


def genkey(size):
    '''
    Key generation
    '''
    ssize = str(size)
    if ssize not in KEY_TYPES:
        raise ValueError

    key = getrandbits(KEY_TYPES[ssize]["size"])

    return key.to_bytes(size // 8, 'little', signed=False)


def encrypt(readable, writable, key, moo=MoO.CBC, iv=None):
    '''
    AES encryption
    (see https://en.wikipedia.org/wiki/Advanced_Encryption_Standard#High-level_description_of_the_algorithm)
    '''
    keysize = str(len(key) * 8)
    if keysize not in KEY_TYPES:
        raise ValueError

    rounds = KEY_TYPES[keysize]["rounds"]
    expkey = _key_expansion(key, KEY_TYPES[keysize])

    # split the expansion key in chunks of size 16 to speedup _add_round_key
    ks = len(expkey) // 16
    expkeys = [expkey[i*NB*NB:(i+1)*NB*NB] for i in range(ks)]

    for block in _encrypt_moo(readable, writable, moo=moo, iv=iv):
        _add_round_key(block, expkeys[0])

        for r in range(1, rounds):
            _sub_bytes(block)
            _shift_rows(block)
            _mix_columns(block)
            _add_round_key(block, expkeys[r])

        _sub_bytes(block)
        _shift_rows(block)
        _add_round_key(block, expkeys[rounds])

        # writable.write(_block2bytes(block))


def decrypt(readable, writable, key, moo=MoO.CBC):
    '''
    AES decryption
    (see https://en.wikipedia.org/wiki/Advanced_Encryption_Standard#High-level_description_of_the_algorithm)
    '''
    keysize = str(len(key) * 8)
    if keysize not in KEY_TYPES:
        raise ValueError

    rounds = KEY_TYPES[keysize]["rounds"]
    expkey = _key_expansion(key, KEY_TYPES[keysize])

    # split the expansion key in chunks of size 16 to speedup _add_round_key
    ks = len(expkey) // 16
    expkeys = [expkey[i*NB*NB:(i+1)*NB*NB] for i in range(ks)]

    for block in _decrypt_moo(readable, writable, moo):
        _add_round_key(block, expkeys[rounds])

        for r in range(rounds - 1, 0, -1):
            _shift_rows_inv(block)
            _sub_bytes_inv(block)
            _add_round_key(block, expkeys[r])
            _mix_columns_inv(block)

        _shift_rows_inv(block)
        _sub_bytes_inv(block)
        _add_round_key(block, expkeys[0])

        # writable.write(_block2bytes(block))


# main program
if __name__ == "__main__":
    import sys

    if len(sys.argv) < 2:
        print(__doc__.format(sys.argv[0]), file=sys.stderr)
        sys.exit(1)

    if sys.argv[1] == "genkey":
        if len(sys.argv) < 3:
            print(__doc__.format(sys.argv[0]), file=sys.stderr)
            sys.exit(1)

        sys.stdout.buffer.write(genkey(int(sys.argv[2])))

    elif sys.argv[1] == "encrypt":
        if len(sys.argv) < 3:
            print(__doc__.format(sys.argv[0]), file=sys.stderr)
            sys.exit(1)

        with open(sys.argv[2], 'rb') as f:
            key = f.read()

        encrypt(sys.stdin.buffer, sys.stdout.buffer, key)

    elif sys.argv[1] == "decrypt":
        if len(sys.argv) < 3:
            print(__doc__.format(sys.argv[0]), file=sys.stderr)
            sys.exit(1)

        with open(sys.argv[2], 'rb') as f:
            key = f.read()

        decrypt(sys.stdin.buffer, sys.stdout.buffer, key)

    else:
        print(__doc__.format(sys.argv[0]), file=sys.stderr)
        sys.exit(1)