| YAZC(1) | General Commands Manual | YAZC(1) |
yazc - yet another zip cracker
yazc [-h] [-V]
yazc COMMAND OPTIONS... FILE
yazc cracks password protected zip files. Three attack methods are supported: bruteforce, dictionary and plaintext.
Note: Only files encrypted using the legacy Pkware encryption method are supported.
The bruteforce command tries every possible character combination. A general rule of thumb is to use this command when you suspect the password to be 8 characters or less.
The dictionary command reads passwords from a text file (or stdin if no file argument is provided). It is assumed that each password is separated by a newline.
The plaintext command uses a known vulnerability in the pkzip stream cipher to find the internal representation of the encryption key. To use this attack type, you need at least 13 known plaintext bytes from any file in the archive. Generally, this means that you need to obtain at least 13 bytes of the compressed stream before it was encrypted.
The plaintext command expects two file arguments along with the corresponding offsets separated by colons. The first file argument is the plaintext filename and offsets:
The second file argument is the encrypted archive filename and offsets (this time including the offset of the first byte of the cipher):
The info command lists the filenames, offsets and the encryption header for each file in the archive. This is useful to determine what configuration to pass to the plaintext command.
Use a bruteforce attack on file archive.zip using only lower case letters and distribute the load to 8 threads:
yazc bruteforce -a -t8 archive.zip
Use a dictionary attack on file archive.zip and use passwords from rockyou.txt:
cat rockyou.txt | yazc dictionary archive.zip
Use a plaintext attack on archive.zip. Take plaintext bytes 100 to 650 and map them to ciphertext bytes 112 to 662. Use these bytes to reduce the number of keys and perform the attack. Once the intermediate key is found, decrypt the rest of the cipher (begins at offset 64) to get the internal representation (the encryption key derived from the password). If possible the actual (or equivalent) password will also be recovered and printed.
yazc plaintext plain.bin:100:650 archive.zip:112:662:64
Marc Ferland <marc.ferland at gmail dot com>
Part of this software was inspired by fcrackzip by Marc Lehmann and pkcrack by Peter Conrad. The original plaintext algorithm was developed by Eli Biham and Paul C. Kocher.