読者です 読者をやめる 読者になる 読者になる

/home/cympfh/

はてなブログはクソなのでやめます => https://hackmd.io/s/SyQBwu6Kg#

SECCON 2015 - Crypt 100 Unzip

Mon Dec 7 14:27:37 JST 2015

SECCON 2015 - Crypt 100 Unzip

既知平文攻撃 (Known-plaintext attack; KPA)

https://en.wikipedia.org/wiki/Known-plaintext_attack

これを使えるツールは pkcrack (他にある?)

設定

   echo '{SECRET FLAG 141306}' > flag
   wget -O backnumber09.txt http://2014.seccon.jp/mailmagazine/backnumber09.txt
   zip -e flag.zip flag backnumber09.txt
Enter password:
Verify password:
  adding: flag (stored 0%)
  adding: backnumber09.txt (deflated 60%)
   rm flag
   ls
backnumber09.txt  flag.zip

解読

   zip a.zip backnumber09.txt
   ls
a.zip  backnumber09.txt  flag.zip
   ~/Tools/pkcrack-1.2.2/src/pkcrack -C 100.zip -c backnumber09.txt -P a.zip -p backnumber09.txt -d b.zip
   unzip b.zip
Archive:  b.zip
extracting: flag
replace backnumber09.txt? [y]es, [n]o, [A]ll, [N]one, [r]ename: A
inflating: backnumber09.txt
   cat flag
{SECRET FLAG 141306}