Solution for the last flareon2021 challenge

wizardcult.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
import sys

table = [90, 132, 6, 69, 174, 203, 232, 243, 87, 254, 166, 61, 94, 65, 8, 208, 51, 34, 33, 129, 32, 221, 0, 160, 35, 175, 113, 4, 139, 245, 24, 29, 225, 15, 101, 9, 206, 66, 120, 62, 195, 55, 202, 143, 100, 50, 224, 172, 222, 145, 124, 42, 192, 7, 244, 149, 159, 64, 83, 229, 103, 182, 122, 82, 78, 63, 131, 75, 201, 130, 114, 46, 118, 28, 241, 30, 204, 183, 215, 199, 138, 16, 121, 26, 77, 25, 53, 22, 125, 67, 43, 205, 134, 171, 68, 146, 212, 14, 152, 20, 185, 155, 167, 36, 27, 60, 226, 58, 211, 240, 253, 79, 119, 209, 163, 12, 72, 128, 106, 218, 189, 216, 71, 91, 250, 150, 11, 236, 207, 73, 217, 17, 127, 177, 39, 231, 197, 178, 99, 230, 40, 54, 179, 93, 251, 220, 168, 112, 37, 246, 176, 156, 165, 95, 184, 57, 228, 133, 169, 252, 19, 2, 81, 48, 242, 105, 255, 116, 191, 89, 181, 70, 23, 194, 88, 97, 153, 235, 164, 158, 137, 238, 108, 239, 162, 144, 115, 140, 84, 188, 109, 219, 44, 214, 227, 161, 141, 80, 247, 52, 213, 249, 1, 123, 142, 190, 104, 107, 85, 157, 45, 237, 47, 147, 21, 31, 196, 136, 170, 248, 13, 92, 234, 86, 3, 193, 154, 56, 5, 111, 98, 74, 18, 223, 96, 148, 41, 117, 126, 173, 233, 10, 49, 180, 187, 186, 135, 59, 38, 210, 110, 102, 200, 76, 151, 198]
key   = [97, 49, 49, 95, 109, 89, 95, 104, 111, 109, 49, 101, 115, 95, 104, 52, 116, 51, 95, 98, 52, 114, 100, 115]

def encrypt(plaintext):
  ciphertext = [0] * len(plaintext)
  for i in range(len(plaintext)):
    k = key[i % len(key)]
    if (i&1):
      k = (k ^ -1) & 255

    r = table[k ^ table[plaintext[i]]]
    if (r&128):
      r ^= 66

    ciphertext[i] = (r ^ -1) & 255
  return ciphertext

def decrypt(ciphertext):
  plaintext = [0] * len(ciphertext)
  for i in range(len(ciphertext)):
    c = (ciphertext[i] ^ -1) & 255
    if (c&128):
      c ^= 66

    k = key[i % len(key)]
    if (i&1):
      k = (k ^ -1) & 255

    plaintext[i] = table.index(table.index(c) ^ k)
  return plaintext

pt = decrypt(open("ciphertext.raw", "rb").read())
open("flag.png", "wb").write(bytearray(pt))