# Some Number Theory

Let $x_n$ be the remainder when $x$ is divided by $n.$ Compute the sum of all positive integers that satisfy

# Another Improper Integral Problem

Evaluate $\displaystyle\int_1^\infty\frac{dx}{e^{x+1}+e^{3-x}}$. (Source: Putnam)

Admittedly, this problem took me an embarrasingly long time to solve (3 hours). Nonetheless, I had fun playing with this particular integral.

For this particular problem, it actually turns out that a symmetric nature is extremely helpful in successfully integrating.

Full PoC w/ abitrary code execution: Link to Issue

Update: The vulnerability has been partially fixed; however, the patch unintentionally removes desired functionality as stated here.

Not too long ago, I was casually perusing my way through GitHub and found the Threadtear Java bytecode deobfuscator. For those of you who don’t know, I have a strong interest for Java bytecode-related projects — especially when deobfuscation and obfuscation are involved.

There’s a warning on the README.md of the repository which specifically informs the user it is possible to successfully execute arbitrary code through the deobfuscator for malicious purposes. So of course, I decided to take up the challenge and create a proof of concept of an ACE exploit in Threadtear.

# Math Obfuscation Of Java Bytecode

Earlier today, I visited the Tigress C obfuscator website today (I haven’t for awhile) and it looks much nicer now ;). Anyways, something that particularly interested me was Tigress’s page on EncodeArithmetic. Since I, a maintainer of a Java bytecode obfuscator, am always looking for cool things to try, found the book they linked of interest.