Writeup for Crypto Problems in CISCN 2019

Writeup for all the crypto challenges in CISCN Pre-qualification 2019 (2019-04-20 09:00 +36h).
- (easy) puzzles: solve easy math and physics problems
- (easy) part_des: decrypt DES with round n encoding result
- (easy) warmup: exploit the repeated AES-CRT counter to find the message
- (easy) Asymmetric: crack a modified RSA encryption by extracting n