Python ZIP Password Cracking Scripts: Encoding Fixes and Single/Multithreaded Brute‑Force Techniques

The article provides a collection of Python scripts for cracking ZIP file passwords, addressing Chinese filename encoding problems and offering single‑threaded, multithreaded, and dictionary‑based brute‑force approaches.

Encoding fix : To resolve garbled Chinese filenames inside ZIP archives, modify zipfile.py so that when the flag 0x800 is set the filename is decoded as UTF‑8, otherwise decode it as GBK. Example:

<code>if flags & 0x800:
    # UTF-8 file names extension
    filename = filename.decode('utf-8')
else:
    # Historical ZIP filename encoding
    filename = filename.decode('gbk')  # 把cp437修改为gbk
</code>

Another location where the same change is needed uses fheader[_FH_GENERAL_PURPOSE_FLAG_BITS] and fname.decode('utf-8' or 'gbk') :

<code>if fheader[_FH_GENERAL_PURPOSE_FLAG_BITS] & 0x800:
    # UTF-8 filename
    fname_str = fname.decode("utf-8")
else:
    fname_str = fname.decode("gbk")   # 把原来的cp437更改为gbk
</code>

Single‑threaded numeric brute‑force : This script iterates over a numeric password range (default 1–1,000,000) and attempts extraction until the correct password is found.

<code>import zipfile, os, time, sys
os.chdir(r'C:\Users\asuka\Desktop\123')
start_time = time.time()

def get_zipfile():
    for file in os.listdir():
        if file.endswith('.zip'):
            return file

def extract():
    file = get_zipfile()
    zfile = zipfile.ZipFile(file)
    for num in range(1, 1000000):
        try:
            pwd = str(num)
            zfile.extractall(path='.', pwd=pwd.encode('utf-8'))
            print('解压密码是：', pwd)
            print('单线程破解压缩包花了%s秒' % (time.time() - start_time))
            sys.exit(0)
        except Exception:
            pass
if __name__ == "__main__":
    extract()
</code>

Single‑threaded alphanumeric brute‑force : Uses a custom iterator to generate random passwords of variable length.

<code>class MyIter(object):
    word = "abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    def __init__(self, min_len, max_len):
        self.min_len = min(min_len, max_len)
        self.max_len = max(min_len, max_len)
    def __iter__(self):
        return self
    def __next__(self):
        result_word = ''
        for i in range(0, random.randint(self.min_len, self.max_len)):
            result_word += random.choice(MyIter.word)
        return result_word

def extract():
    start_time = time.time()
    zip_file = zipfile.ZipFile('1.zip', 'r')
    for password in MyIter(password_min, password_max):
        try:
            zip_file.extractall(path='.', pwd=str(password).encode('utf-8'))
            print('压缩密码为：', password)
            print('破解压缩包花了%s秒' % (time.time() - start_time))
            sys.exit(0)
        except Exception:
            pass
</code>

Multithreaded dictionary attack : Reads passwords from a user‑specified text file and launches a thread for each candidate.

<code>def extractfile(zip_file, password):
    try:
        zip_file.extractall(path='.', pwd=str(password).encode('utf-8'))
        print('[+]' + zip_file + ' 解压密码是：', password)
        sys.exit(0)
    except Exception:
        pass

def main(password_file):
    for file in os.listdir():
        if file.endswith('.zip'):
            zip_file = zipfile.ZipFile(file)
            with open(password_file) as pf:
                for line in pf.readlines():
                    password = line.strip('\n')
                    Thread(target=extractfile, args=(zip_file, password)).start()
</code>

Combined 3‑in‑1 script : Supports pure numeric, alphanumeric, and dictionary attacks in a single program, with user prompts for password length ranges, working directory, and dictionary file selection.

<code># (The script includes functions ready_work(), get_zipfile(), MyIter, extract(), password_file_baopo(), run() etc.)
# It guides the user through selecting mode 1 (numeric), mode 2 (alphanumeric), or mode 3 (dictionary) and then executes the corresponding brute‑force routine.
</code>

The article concludes with screenshots of the three operation modes and a link to the original CSDN blog post.