Crack Zip Password

When unzipping archived files, we're sometimes asked the passphrase. We may be able to crack the password with various ways.

John The Ripper

Format the archived file to make the John to recognize it, then crack the hash using John.

zip2john example.zip > hash.txt
john --wordlist=wordlist.txt hash.txt

Fcrackzip

# -u: unzip
# -D: dictionary
# -p: strgin as initial password/file
fcrackzip -u -D -p passwords.txt sample.zip

Bkcrack

bkcrack is useful for cracking legacy zip encryption with a known plaintext attack.

Download the Tool

wget https://github.com/kimci86/bkcrack/releases/download/v1.5.0/bkcrack-1.5.0-Linux.tar.gz
tar -xf bkcrack-1.5.0-Linux.tar.gz
cd bkcrack-1.5.0-Linux.tar.gz

Recover Internal Keys

First we check what files in the target zip file.

# List entries
./bkcrack -L encrypted.zip

Assume the encrypted.zip contains the secret.key file and we know that it contains the "secret is" string. Then we need to create a plain file with the same string "secret is".

echo -n "secret is" > plainfile

Now crack the keys using these files.

./bkcrack -C encrypted.zip -c secret.key -p plainfile

For example, we get the result 8257499e 175bb63c fcbd5ff2. We can recover the password by running the following command.

./bkcrack -C encrypted.zip -c secret.key -p plainfile -k 8257499e 175bb63c fcbd5ff2 -d result.txt

After that, result.txt is generated so we can see the content of the file.