HNCTF部分总结复现

# H&NCTF 2025

misc2.星辉骑士

打开是有一张图片的docx，docx格式直接改zip解压

word-media

发现flag.zip 解压要密码 试着是否为伪加密 嗦一下发现是 直接修复了 解压修复之后的 就可以看到10个txt文本 都打开没有什么实际含义（垃圾邮件），看了wp说这是一种加密方式（按顺序放进网站）spammimic - decode

111.txt : ashjdsahd

222.txt: asdjhuasdvghj

333.txt :sdfsdfsfasfwq

444.txt: asdasdadadadwdf

555.txt: flag{this_is_fake_lg}

666.txt: flag{this_is_fake_flg}

777.txt: flag{this_is_fakeg}

888.txt:flag{this_is_fake_flag}�

999.txt:flag{0231265452-you-kn*w-spanmimic}

misc6芙宁娜的照片

Brainfuck加密Brainfuck/OoK加密解密 - Bugku CTF平台

O&NPTF{Y0u_yepognizeq_the_Couphu's_psog.}

雏形已经出来了

图片梭一把 发现RGB那里有key：H&N2025

有密钥且不改变明文长度的加密方式-试维吉尼亚维吉尼亚加密/解密 - Bugku CTF平台

H&NCTF{Y0u_recognised_the_Chuchu's_plot.}

CRYPTO5哈基coke

题目打开是python代码和一张en_flag.png 说明该图片经过加密

写一个脚本把他还原一下

import cv2
import numpy as np
from PIL import Image
import matplotlib.pyplot as plt
​
​
def arnold_decode(encrypted_image, shuffle_times, a, b):""" Arnold逆变换解密图像Args:encrypted_image: 加密后的图像shuffle_times: 加密时的置乱次数a, b: Arnold变换参数Returns:decrypted_image: 解密后的图像"""decrypted_image = np.zeros_like(encrypted_image)h, w = encrypted_image.shape[0], encrypted_image.shape[1]N = h  # 假设图像为正方形
​# 计算逆变换参数# 逆变换公式:#   ori_x = ((a*b+1)*new_x - b*new_y) mod N#   ori_y = (-a*new_x + new_y) mod N
​for time in range(shuffle_times):for new_x in range(h):for new_y in range(w):# 应用逆变换公式ori_x = ((a * b + 1) * new_x - b * new_y) % Nori_y = (-a * new_x + new_y) % N
​# 处理负数情况if ori_x < 0:ori_x += Nif ori_y < 0:ori_y += N
​decrypted_image[ori_x, ori_y, :] = encrypted_image[new_x, new_y, :]
​encrypted_image = np.copy(decrypted_image)
​# 转换为无符号8位整数（OpenCV格式）decrypted_image = decrypted_image.astype(np.uint8)cv2.imwrite('de_flag.png', decrypted_image, [int(cv2.IMWRITE_PNG_COMPRESSION), 0])return decrypted_image
​
​
# 读取加密后的图像
encrypted_img = cv2.imread('en_flag.png')
if encrypted_img is None:print("[!] 无法读取加密图像，请确保en_flag.png存在")
else:# 执行解密（参数与加密时一致）decrypted_img = arnold_decode(encrypted_img, shuffle_times=6, a=9, b=1)
​# 显示结果plt.figure(figsize=(12, 6))plt.subplot(121), plt.imshow(cv2.cvtColor(encrypted_img, cv2.COLOR_BGR2RGB))plt.title('加密图像'), plt.axis('off')plt.subplot(122), plt.imshow(cv2.cvtColor(decrypted_img, cv2.COLOR_BGR2RGB))plt.title('解密图像'), plt.axis('off')plt.tight_layout()plt.show()
​print("[+] 解密完成，结果保存为de_flag.png")

H&NCTF{haji_coke_you_win}