Looking Towards Summer: Concolic Execution, Fuzzy Panda, and More

It’s always bothered me that MIT or MIT Lincoln Lab didn’t submit anything to DARPA’s Cyber Grand Challenge. With all the smart people, such as my advisor, Armando Solar-Lezama, working on program analysis and formal methods (which I currently know nothing about), I would have expected that we could create a strong Cyber Reasoning System worthy of CGC.

That’s sort of what I will be working on this summer at Lincoln and probably writing my thesis on. But I’m very new to the field and have just started diving in.

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Matasano Crypto Challenges, Set 6

The last of the original crypto challenges… here we go!

Challenge 41 Implement unpadded message recovery oracle

Unpadded RSA is homomorphic, meaning that, if operations like multiplication and addition are carried out on ciphertext, it is as if the same operation were applied to the plaintext.

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Generating and Interpreting Bytecode for MITScript — Using Rust

Well, this was my first foray into the world of Rust, the systems language that is Mozilla’s precious baby. And what better way to learn this hip new language than to write an MITScript bytecode interpreter for Computer Language Engineering?

Rust was not gentle for this first-time developer. It does so much to protect you that my first attempt writing a few hundred lines of code resulted in the same number of compiler errors, and I needed a lot of help from my team to just get anything to compile. For this reason, it’s not great for iterating quickly if you aren’t very experienced already. But, I’m licking my chops at the fact that the end result will be much safer, and hopefully faster, than our classmates’ C++ compilers. This post will be about the struggles I encountered as a Rust newbie, as well as the fun of generating/interpreting MITScript bytecode.

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Writing a C++ Interpreter for MITScript

Lab 2 in 6.035 was very satisfying and very fun. After creating the parser/lexer in Lab 1, we got to put our Abstract Syntax Tree to work — we created an interpreter to actually execute valid MITScript! By the end of this lab, we will be able to write arbitrarily complex programs and have them parsed and run.

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Upcoming Blog Posts — Stay Tuned!

I’ve been insanely busy with a bunch of cool things, which means both more blog content, but also quite a large latency before I get around to writing them.

Here’s what I’ve been up to, and what awesome posts/series you can expect in the coming weeks:

  • 6.115 Labs and Final project — Masterlock combo breaker?
  • 6.857 Final project — Boston Symphony Orchestra iPad app pentest
  • CTFs — MITCTF, Cambridge2Cambridge
  • 6.035 MITScript interpreter in Rust

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Starting a New Security Club at MIT

fortenforge, Devin Neal, and I decided that MIT needed more of a student security community on campus. So, we started TechSec in February 2017! We host weekly meetings on Monday nights and try to get students to compete with us in CTFs on weekends.

You can find our meeting/workshop notes, which we laboriously compile for the benefit of our club members, here. So far, we’ve been holding introduction to reverse engineering and binary workshops. We have a lot more planned, including interesting guest speakers.

Matasano Crypto Challenges, Set 1

Challenge 1.1 Convert hex to base64

The first challenge is pretty straightforward, using python’s built-in functions or pwntools, as I use heavily in these challenges.

The functions a2b_hex, unhexlify, and ''.decode("hex") all do the same thing. They take in an ascii string of the form “[0-9a-f]*” and decode it. The string decodes to
I'm killing your brain like a poisonous mushroom. We can then use binascii.b2a_base64() to convert the byte string to a base64 representation.

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Matasano Crypto Challenges, Set 2

Challenge 9 Implement PKCS#7 padding

As the challenge states, “A block cipher transforms a fixed-sized block (usually 8 or 16 bytes) of plaintext into ciphertext. But we almost never want to transform a single block; we encrypt irregularly-sized messages.”

The PKCS#7 padding scheme will append the number of bytes of padding to the end of the block. I use the pwntools pack() function to pack the number of padding bytes.

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