May
01

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.

May
01

Google CTF – Wolf Spider (Crypto 125)

Continuing on from Eucalypt Forest – can you break Message Authentication in Wolf Spider wolf.py Summary: forging signatures by exploiting CBC padding oracle and hash length extenstion

Apr
24

PlaidCTF 2016 – sexec (Crypto 300)

If you need to securely grant execution privileges, what better way to do it than sexec? This is running on sexec.pwning.xxx:9999 sexec.tar.gz Summary: attacking a small instance of Ring-LWE based cryptosystem with Babai’s Nearest Vector algorithm.

Apr
18

PlaidCTF 2016 – Radioactive (Crypto 275)

We just got this fancy new cryptographic device and it seems to work great… for the most part. But sometimes the values it gives me are wrong. Maybe you could take a look for me. radioactive.tar.bz2 Summary: fault attack on RSA signature (not RSA-CRT)

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)

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