Jul 20
If you haven’t yet registered for our 2020 edition of CyBRICS CTF, you should. Like previous year, it’s made by SPbCTF meetups crew (guys from MSLC / LC↯BC, SiBears, PeterPEN, Yozik), and we invite all teams to play. Unlike previous year, this one is Lite — single online Jeopardy round, everyone is eligible, and you get prizes without playing Attack-Defense! (which is rare nowadays) The same great set of …
Sep 30
Is post quantum cryptography too complex for you? wrong_ring.sage Summary: Ring-LWE with small error, hidden under a number field
Aug 11
Brief solution ideas to the least solved Crypto CTF challenges.
Jul 13
We, in SPbCTF meetups crew (guys from LC↯BC, SiBears, PeterPEN, Yozik), were invited to make a CTF together with some BRICS countries universities. So we made one — and invite everyone to compete, have fun and win some prizes in CyBRICS CTF 2019. This one continues the tradition of hack you events, but this time …
Jun 27
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 key which is the initial state. Here is the nonlinear filtering function: f(v) = v[0] ^ v[1] ^ v[2] …
Oct 05
As a tradition, every fall we host a fun lightweight Jeopardy CTF for our freshmen to attract them into all the CTFey goodness. This one will be our fifth year (holy shit!) We invite everyone to check out hack you ’17 this year. Just as always, two separate scoreboards: one for SPbCTF meetups, one for …
Sep 04
Scripts with short explanations: BabyPinhole (crypto 163) Liar’s Trap (crypto/ppc 281) Palindrome Pairs – Challenge Phase (ppc 63+337)
Jul 09
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 truncated-to-MSB LCG with top-down bit-by-bit search.
Jun 19
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.
Jun 19
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 old one) Rubik Bleichenbacher’s Lattice Task (full writeup here)
Mar 20
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, could you help him to get back his seed? We can not save the game, but we may be able …
Mar 20
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 Summary: breaking a linear and an LCG-style exponential PRNGs.
Mar 20
Make bad politicians resign! nc 78.46.224.72 2048 files Summary: factorization-based attack on a signature method
Oct 15
Remember hack you CTF? Yeah, that random event that we throw for our freshmen and everyone interested. We’re hosting a new one. It’s fall already and that means the new CTF season is starting, and so is the new academic year in the universities. This is the time when we want to attract more freshmen …
Oct 11
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.