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[Viettel Mates CTF 2018] Viettel Store Write-up (Crypto100)

Thank God It’s Weekend! Let’s go shopping! Source: https://drive.google.com/file/d/167se6uAZ48Bt5k34m37LOK1tD2wt3Tsb/view?usp=sharing nc 13.251.110.215 10001 Let’s connect to the server and see what’s going on before we move on to the source code.

It welcomes us with a shop interface where we… Continue Reading →

[Viettel Mates CTF 2018] Web Token Write-up (Crypto100)

Source code: https://drive.google.com/open?id=1uLeYsqnLNVNMurQ11q2ustvW2o_V7IPl Server: http://ec2-13-229-142-46.ap-southeast-1.compute.amazonaws.com:9999 The website simply asks for our name, then it welcomes us and asks whether we are administrator or not. It decides if we are administrator or not using the cookie created which is named as… Continue Reading →

[Angstrom CTF 2018] OFB Write-up (Crypto120)

defund made a simple OFB cipher, if you can even call it that. Here’s the source and the encrypted flag. Let’s look at the encryption script first.

First, it reads the flag.png and if the total number of bytes… Continue Reading →

[XIOMARA CTF 2018] Custom HEN Cipher Write-up (Crypto50)

Ragnar & Lagertha are two secret agents of Valhalla wants to share a secret message but could not place the trust on basic ciphers so they decided to come up with their own cipher We have managed to get the… Continue Reading →

[XIOMARA CTF 2018] Giveaway Write-up (Crypto150)

Hey! We at Xiomara would love to giveaway the flag to you. But, we can’t now, because someone just stole it from us and tried sending it to our rival, Jack. Our super strong web guy here came to the… Continue Reading →

[SECCON CTF 2017] Vigenere3d Write-up (Crypto100)

—– Vigenere3d.py import sys def _l(idx, s): return s[idx:] + s[:idx] def main(p, k1, k2): s = “ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz_{}” t = [[_l((i+j) % len(s), s) for j in range(len(s))] for i in range(len(s))] i1 = 0 i2 = 0 c =… Continue Reading →

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