Full writeup: [https://github.com/happysox/CTF_Writeups/tree/master/XMAS_CTF_2018/friedrich](https://github.com/happysox/CTF_Writeups/tree/master/XMAS_CTF_2018/friedrich)
### Summary
* XOR the first 200 bytes with 13 to repair the original elf* Patch the anti-debug instructions* Dynamic analysis* Solve linear equation `Ax=b` where   * A is a 36*36 matrix containing scalars found in the runtime memory   * b is a vector with 36 sums found the same way  * x is the flag