Known-plaintext attack
Keynote:
- cracking ZIP Files
- you need to have one of the original files contained in the encrypted archive
Reference:
- https://www.hackthis.co.uk/articles/known-plaintext-attack-cracking-zip-files
Tools:
- pkcrack
一開始先確認 facebook.zip 為 zip 檔
$ file facebook.zip
facebook.zip: Zip archive data, at least v1.0 to extract
打開後發現有加密，試著看壓縮檔裡面有什麼檔案
$ unzip -l facebook.zip
Archive: facebook.zip
Length Date Time Name
-------- ---- ---- ----
38 07-15-15 18:15 key.txt
0 07-15-15 18:13 p960x960/
26664 10-30-13 08:19 p960x960/851556_443281069111871_602278786_n.png
-------- -------
26702 3 files
藉由網路上的教學
you need to have one of the original files contained in the encrypted archive What you are going to do with it is you are going to compress it using the same compression method as the protected file. Remember this, otherwise it won’t work. So after you do that, move both your zip files, the encrypted one and the plaintext zip
去 google 找 851556_443281069111871_602278786_n.png
壓縮該檔案（包含完整路徑）
$ zip -r plaintext.zip p960x960/851556_443281069111871_602278786_n.png
$ file plaintext.zip
Archive: plaintext.zip
Length Date Time Name
-------- ---- ---- ----
26664 07-25-15 00:09 p960x960/851556_443281069111871_602278786_n.png
-------- -------
26664 1 file
執行 pccrack
pkcrack -C facebook.zip -c “p960x960/851556_443281069111871_602278786_n.png” -P plaintext.zip -p “p960x960/851556_443281069111871_602278786_n.png” -d decrypted.zip -a
解壓縮 decrypted.zip，裡面的 key.txt 就放著 flag