Oct
11

HITCON 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.

Oct
10

HITCON CTF QUALS 2016 – PAKE / PAKE++ (Crypto 250 + 150)

pake1.rb pake2.rb Summary: attacking password-based key exchange schemes based on SPEKE with MITM.

Oct
03

TUM CTF 2016 – Shaman (Crypto 500)

Oh great shaman! Somehow the village idiot got his hands on this fancy control machine controlling things. Obviously, we also want to control things (who wouldn’t?), so we reverse-engineered the code. Unfortunately, the machine is cryptographically protected against misuse. Could you please maybe spend a few seconds of your inestimably valuable time to break that… Continue reading »

Oct
02

TUM CTF 2016 – Tacos (Crypto 400)

All my fine arts and philosophy student friends claim discrete logarithms are hard. Prove them wrong. nc 104.198.63.175 1729 vuln_tacos.py Summary: bypassing Fermat primality test with Carmichael numbers and solving discrete logarithm using Pohlig-Hellman algorithm.

Sep
19

CSAW 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 signatures, factoring using private exponent exposure.

Sep
05

Tokyo Westerns/MMA CTF 2016 – Backdoored Crypto System (Reverse+Crypto 400)

Get the flag. bcs.7z $ nc bcs.chal.ctf.westerns.tokyo 3971 Summary: recovering AES key from partial subkey leaks.

Sep
05

Tokyo 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.

May
03

Google CTF – Woodman (Crypto 100)

How honest are you? Running here Summary: breaking a weak PRNG

May
01

Google 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.

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.

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