Mar
14

0CTF 2016 Quals – Equation (Crypto 2 pts)

Here is a RSA private key with its upper part masked. Can your recover the private key and decrypt the file? equation.zip Summary: recovering RSA key from part of the private key.

Mar
13

0CTF 2016 Quals – RSA? (Crypto 2 pts)

It seems easy, right? rsa.zip Tip: openssl rsautl -encrypt -in FLAG -inkey public.pem -pubin -out flag.enc Summary: factoring 300-bit modulus into 3 primes, extracting cube roots.

Sep
07

MMA CTF 2015 – Motto Mijikai Address (Crypto/Web 100+300)

Login as admin and get the flag1. mmaddress.7z Summary: breaking HMAC-CRC512

May
27

CONFidence CTF 2015 – RSA2 (Crypto 500)

Find the flag data Summary: cube attack + recover python’s MersenneTwister state + leak 320/520 LSBs of one of the primes

May
27

CONFidence CTF 2015 – RSA1 (Crypto 400)

Find the flag data Summary: Coppersmith’s short pad attack

May
11

ASIS CTF Quals 2015 – Cross Check (Crypto 350)

The flag is encrypted by this code, can you decrypt it? crosscheck.tar.xz Summary: breaking RSA modulos with related primes.

May
04

VolgaCTF Quals 2015 – CPKC (Crypto 400) writeup

cpkc A home-brewed cryptosystem, should be easy to break. Its keyspace seems to be rather large though… challenge.tar Summary: LLL-based attack on NTRUEncrypt-like cryptosystem.

Apr
20

PlaidCTF 2014 wheeeee writeup

Although it seems like The Plague’s messaging service is secure, there are bound to be bugs in any 20th century crypto system. We’ve recovered a version of the block cipher The Plague implemented. Use their online encryptor tool, at 54.82.75.29:8193, to break the cipher and figure out Plague’s secret plans. NOTE: When the service sends… Continue reading »

Apr
19

PlaidCTF 2014 parlor writeup

The Plague is running a betting service to build up funds for his massive empire. Can you figure out a way to beat the house? The service is running at 54.197.195.247:4321.

Apr
17

PlaidCTF 2014 RSA writeup

Our archaeologists recovered a dusty and corrupted old hard drive used by The Plague in his trips into the past. It contains a private key, but this has long since been lost to bitrot. Can you recover the full key from the little information we have recovered?

Mar
02

Boston Key Party CTF – Differential Power (Crypto 400)

we hooked up a power meter to this encryption box. we don’t know the key. that’s what we want to know. you can encrypt any string of 8 characters on the service http://54.218.22.41:6969/string_to_encrypt encrypt.asm chall source (released after ctf)

Feb
09

Olympic CTF 2014 GuessGame (300)

Be careful, it’s cheating! nc 109.233.61.11 3126 Summary: discrete logarithm with group oracle

Feb
02

Olympic CTF Sochi 2014 Registration is Open

Let there be Olympics MSLC proudly presents…Alright, do we even need words here? Game starts: February 7th, 2014 16:14 UTC (yeah yeah, those Sochi number freaks… it’s 20:14 in MSK timezone) Game ends: February 9th, 2014 16:14 UTC Sign up: https://olympic-ctf.ru/ Prize set: 1500 USD, 1000 USD, 500 USD. Expect decent tasks. Twenty of them.

Jan
07

Sudden CTF syndrome

Happy new 2014 and merry Orthodox Christmas if you’re religious ;-D Maybe you already know hack you and hack you too, so I won’t even say that hack you is an individual CTF that we originally held for our university freshmen and opened it for everyone interested in the world. Couple days after this New… Continue reading »

Jun
17

Defcon CTF Quals 2013 – All Web Challenges (3dub)

Summary: 3dub (1) – babysfirst: SQLite SQL injection 3dub (2) – badmedicine: Stream cipher bit flipping 3dub (3) – hypeman: Rack/Sinatra session secret disclosure 3dub (4) – rememberme: Bruteforce 3dub (5) – worsemedicine: Block cipher bit flipping

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