[WhiteHat Challenge 04] crypto02 | Ph03nix Team

Ph03nix Team

H4ck f0r fun

Home About Us
[WhiteHat Challenge 04] crypto02
BlackWings

Question

Find flag in http://chall04-crypto02.wargame.whitehat.vn


We have a script:


With that I can know AES ECB mode and try to find len(flag)



When input 8 bytes I have 3 block cipher and 2 block for 7 bytes so I can calculate len(flag)

len('something!') + 8 + len(flag) + 16 bytes padding = 3*16  
 ==> len(flag) = 14


Because blocks have same encryption so I can use padding to bruteforce flag

Block 1: “something!” + ‘a’*37 + 1 character bruteforce
Block 2: “something!” + ‘a’*37 + flag[0]

Repeat like that I got flag





Run babe runnnnnnn =]]]]]]]]]

Flag: [*] WhiteHat{1ffe5f92c181a89dd267cfd4b6ec2c80c6202391} [*]