pyzipper

Install the pyzipper package using pip to enable AES encrypted zip file support in Python.

pip install pyzipper

The library supports two versions of the WinZip AES specification, primarily differing in how they handle CRC (Cyclic Redundancy Check) values:

• WZ_AES_V1: Includes the CRC in the local file header. This is useful for integrity but can leak information about the contents of very small files.
• WZ_AES_V2: Does not use the CRC (it is set to 0). This is more secure for small files. This version is automatically used if the compression method is ZIP_BZIP2 because BZIP2 has its own integrity checks.

You can force a version using force_wz_aes_version in the encryption configuration, or use conditionally_include_crc to switch between them based on file size.

From pyzipper v0.4.0 onwards, CRC32 values are not included in file headers by default to prevent information leakage about small files. You can conditionally enable CRC32 inclusion for files that meet a minimum uncompressed size threshold using setencryption() with the conditionally_include_crc and min_bytes_to_include_crc parameters. The recommended minimum for min_bytes_to_include_crc is 20.

with pyzipper.AESZipFile(
    'new_test.zip',
    'w',
    compression=pyzipper.ZIP_LZMA,
) as zf:
    zf.setencryption(
        pyzipper.WZ_AES,
        conditionally_include_crc=True,
        min_bytes_to_include_crc=20,  # Replace with your desired threshold
    )
    ...

You can specify the AES encryption strength (bit length) using the setencryption() method. Supported values for nbits are 128, 192, or 256. The default strength is 256 bits.

import pyzipper

secret_password = b'lost art of keeping a secret'

with pyzipper.AESZipFile('new_test.zip', 
                         'w', 
                         compression=pyzipper.ZIP_LZMA) as zf:
    zf.setpassword(secret_password)
    zf.setencryption(pyzipper.WZ_AES, nbits=256)
    zf.writestr('test.txt', "What ever you do, don't tell anyone!")

For ZIP archives using PKWARE password-based encryption, use the CRCZipDecrypter.

Usage Pattern:

1. Initialize with a ZipInfo object, the password, and the encryption header.
2. Call .decrypt(cypher_bytes) to get the plaintext bytes.

Note: The first 12 bytes of the cypher stream is an encryption header used to strengthen the algorithm.

from pyzipper import CRCZipDecrypter

# zd = CRCZipDecrypter(zinfo, mypwd, encryption_header)
# plain_bytes = zd.decrypt(cypher_bytes)

Use these methods to explore the contents of a ZipFile:

• namelist(): Returns a list of file names in the archive.
• infolist(): Returns a list of ZipInfo instances for all files in the archive.
• getinfo(name): Returns the ZipInfo instance for a specific file name. Raises KeyError if not found.
• printdir(): Prints a formatted table of contents to stdout.

with pyzipper.ZipFile('example.zip', mode='r') as zf:
    # Get names
    print(zf.namelist())
    
    # Get detailed info
    for info in zf.infolist():
        print(f"{info.filename}: {info.file_size} bytes")
    
    # Get specific info
    info = zf.getinfo('data.txt')
    print(info.compress_type)

Write data directly into the archive without using a file on disk. The data can be a str (which will be encoded as UTF-8) or bytes.

zinfo_or_arcname can be a ZipInfo instance or a string representing the filename in the archive.

# Write a string directly
zf.writestr('hello.txt', 'This is some text content')

# Write bytes directly
zf.writestr('data.bin', b'\x00\x01\x02\x03')

# Write using a ZipInfo object for fine-grained control
import time
from pyzipper import ZipInfo

zinfo = ZipInfo('custom.txt')
zinfo.date_time = time.localtime().tm_year, time.localtime().tm_mon, time.localtime().tm_mday, 0, 0, 0
zf.writestr(zinfo, 'Custom metadata content')

You can associate a comment with the entire ZIP archive using the comment property. The comment must be provided as bytes.

Note: If the comment exceeds ZIP_MAX_COMMENT, it will be truncated with a warning.

with pyzipper.ZipFile('example.zip', mode='a') as zf:
    zf.comment = b'This is an archive comment'