CSAW CTF 2012 write-up: CryptoMat (web400)

Here is the description of the challenge:
CryptoMat is a site where you can send encrypted messages to other users. Dog is a user on the site and has the key. Figure out how to get into his account and obtain it.

The first thing we had to do was finding out how the encryption algorithm works. After a few attempts, we discovered that the title wasn’t used for the encryption and that, given a plaintext P and a key k, we have
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The “Million Message Attack” in 15,000 Messages

An article on our paper “Efficient Padding Oracle Attacks on Cryptographic Hardware“, to appear at CRYPTO 2012 this August, has been published today on the New-York Times. The news seems to be bouncing back and forth on many blogs, sometimes imprecise and exaggerated. Our FAQ page should clarify any doubt you might have. If you are curious and you don’t want to go through the full paper, Matthew Green’s blog provides a very nice write-up.

PlaidCTF 2012 write-up: The Game

The following description is provided:

Robots enjoy some strange games and we just can’t quite figure this one out. Maybe you will have better luck than us.

The game offers a choice between two hex strings asking for the “bigger” one. Anyway, it doesn’t appear to be a way to determine which one is bigger just by looking at the values.
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Gran: grsecurity analyser

Our paper about automated analysis of grsecurity has been accepted for presentation at IEEE CSF 2012 at the end of June. In the paper we formalize grsecurity semantics and, based on that, we develop a tool that checks for security flaws inside real grsecurity policies. The paper is based on Marco Squarcina’s undergraduate thesis (tesi triennale).

The gran tool (grsecurity analyser) is available for download here.

CSAW CTF 2011 Write-up: Exploitation bin4

This challenge shares the same source code as the bin2 challenge, but the environment is different:
we need to bypass ASLR and we can’t overwrite the GOT nor the .dtors section (because of RELRO).
We will bypass those protections using a ROP approach.
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