Google CTF – Jekyll (Crypto)
Can you access the admin page? You can look at the crypto here. source.py Summary: finding a preimage for a simple 64-bit ARX-based hash. Here’s the code of the web server: def jekyll32(data, seed):...
View ArticleGoogle CTF – Spotted Wobbegong (Crypto 100)
Are you able to defeat 1024-bit RSA? public.pem Summary: breaking RSA with PCKS v1.5 padding and exponent 3. On the web page we see the two options: get token and check token. It is also said the the...
View ArticleTokyo Westerns/MMA CTF 2016 – Pinhole Attack (Crypto 500)
Decrypt the cipher text with a pinhole. $ nc cry1.chal.ctf.westerns.tokyo 23464 pinhole.7z Summary: attacking RSA using decryption oracle leaking 2 consecutive bits in the middle. In this challenge we...
View ArticleCSAW Quals 2016 – Broken Box (Crypto 300 + 400)
I made a RSA signature box, but the hardware is too old that sometimes it returns me different answers… can you fix it for me?} e = 0x10001 nc crypto.chal.csaw.io 8002 Summary: fault attack on RSA...
View ArticleHITCON CTF QUALS 2016 – Reverse (Reverse + PPC 500)
At least our ETA is better than M$. http://xkcd.com/612/ reverse.bin Summary: optimizing an algorithm using Treap data structure and CRC32 properties. After reverse-engineering the binary, we can...
View ArticleHack.lu 2010 CTF Challenge #18 Writeup
Digital Treasure Chest (300) You were asked to pentest the 1.1 beta-version of the digital treasure chest. Finding an authentication bypass appears to be trivial to you. pirates.fluxfingers.net...
View ArticleHack.lu 2010 CTF Challenge #19 Writeup
Magicwall (400) Captain Hook found the following link after looting his last frigate. He heard that the file flag on this system is worth 400 coins. Give him this file and he will reward you! ssh:...
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Hack.lu 2010 CTF Challenge #10 Writeup
#10 – Chip Forensic To solve this task we have something like this (original image is lost) and hex string: 0B 12 0F 0F 1C 4A 4C 0D 4D 15 12 0A 08 15. What we see on image? Some USB device. Those who...
View ArticleHack.lu 2010 CTF Challenge #7 Writeup
Breiers Deathmatch (150) Schnuce Breier has challenged you to a cryptographer’s deathmatch. Connect to pirates.fluxfingers.net 8007/tcp and get the secret number. $ nc pirates.fluxfingers.net 8007 Hi....
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Hack.lu 2010 CTF Challenge #8 Writeup
Sad Little Pirate (150) Our sad little pirate haes lost his password. It is known that the pirate has just one hand left; his left hand. So the paessword input is quite limited. Also he can still...
View Article33C3 CTF 2016 – beeblebrox (Crypto 350)
Make bad politicians resign! nc 78.46.224.72 2048 files Summary: factorization-based attack on a signature method In this challenge we have access to a signature oracle, who does not sign a special...
View Article0CTF 2017 Quals – OneTimePad 1 and 2
I swear that the safest cryptosystem is used to encrypt the secret! oneTimePad.zip Well, maybe the previous one is too simple. So I designed the ultimate one to protect the top secret! oneTimePad2.zip...
View Article0CTF 2017 Quals – Zer0llvm
Talent Yang loves to customize his own obfuscator. Unfortunately, he lost his seed when he was watching Arsenal’s UEFA game. What a sad day! His team and his seed were lost together. To save him,...
View ArticleGoogle CTF 2017 Quals – Crypto writeups
Scripts with short explanations for all crypto tasks (except RSA) from Google CTF Quals 2017: Crypto Backdoor Introspective CRC Shake It RSA CTF Challenge (no writeup, but I think it’s similar to this...
View ArticleGoogle CTF 2017 Quals – BLT (Bleichenbacher’s Lattice Task – Insanity Check)
A slow descent into the dark, into madness, futility, and despair. BLT.jar (not necessary) STDOUT Flag.java Summary: DSA with short secrets, lattice + meet-in-the-middle attack. In this challenge we...
View ArticlePolictf 2017 – Lucky Consecutive Guessing (Crypto)
We implemented a random number generator. We’ve heard that rand()’s 32 bit seeds can be easily cracked, so we stayed on the safe side. nc lucky.chall.polictf.it 31337 chall.py Summary: breaking...
View ArticleTWCTF 2017 – Solutions for BabyPinhole, Liar’s Trap, Palindrome Pairs Challenge
Scripts with short explanations: BabyPinhole (crypto 163) Liar’s Trap (crypto/ppc 281) Palindrome Pairs – Challenge Phase (ppc 63+337)
View ArticleMidnight CTF 2018 Finals – Snurre128
In this challenge we have a stream cipher based on LFSR and nonlinear filtering function. It has 128-bit LFSR secret state and we are also given 1600 keystream bits. Our goal is simply to recover the...
View Article1st Crypto CTF 2019 – Least Solved Challenges
Brief solution ideas to the least solved Crypto CTF challenges. Midnight Moon We can see that the primes are generated as follows. Let $m$ be the right half of the flag (as an integer) and $l$ be its...
View ArticlePwnThyBytes CTF 2019 – Wrong Ring (Crypto)
Is post quantum cryptography too complex for you? wrong_ring.sage Summary: Ring-LWE with small error, hidden under a number field Let us look at the main part: prime = 1487 degree = 256 q = x^256 +...
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