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8:49 PM 05/17/2020
Description
BE CAREFUL PLAYING WITH THIS IT CAN ENCRYPT YOUR FILES.
As long as you run it on an isolated folder or a VM you should be fine. The purpose of the challenge is to introduce people to the concept of reverse engineering a baby randomware. The main target of the challenge is to write a decryptor using the language of your choice.
P.S. This is for EDUCATIONAL and DEMONSTRATION purposes only, the creator carries no responsibilities if your files get encrypted.
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Shad3 on 1:11 PM 05/24/2020: The bitcoin address is there for demonstration purposes only (if you want to donate to it feel free to) , it belongs to the Free Software Foundation and it was taken from here : https://bitcoinwhoswho.com/blog/2016/02/29/bitcoin-donation-address-rankings/
x0r19x91 on 11:17 AM 05/27/2020: https://paste.ubuntu.com/p/nNm3p2qYMQ/
zed-zahir on 4:58 PM 05/27/2020: the solution I came up with, is you will create one file with null bytes, something like 10 or less, then you let the crypto-ransomware crypt it then you check the encrypted file because when you xor a file with null byte it will give you the key, which here in our situation is '\' 0x5C hex
this technique is called null byte attack
js-on on 4:01 PM 05/31/2020: When running it twice, you'll get file.corona.corona files which are completely unencrypted.
zed-zahir on 10:04 PM 06/05/2020: js-on, good point, I didn't think about it!!
sherhack on 2:29 AM 06/24/2020: Fun crackme, looked for you encrytion code and reversed the XoR operation along with the 0xdeadbeef seed
panzo on 7:12 PM 03/30/2021: Fun to do but the fact that the operation used to crypt can be reverse just by re-iterate is not cool :0
jimsktsmith on 4:21 PM 12/29/2021: Solu : Create txt - simple word like 'a' or 'ab'
Text xor 92
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0xp3rryhu on 11:44 AM 07/17/2025: Pretty cool crackme gj :))
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Solution by 2ourc3:
Write up by 2ourc3 (bushido-sec.com)