This challenge is an almost-exact copycat of VolgaCTF Quals 2015 – CPKC.

You can find an excellent writeup by team More Smoked Leet Chicken here: [http://mslc.ctf.su/wp/volgactf-quals-2015-cpkc-crypto-400-writeup/](http://mslc.ctf.su/wp/volgactf-quals-2015-cpkc-crypto-400-writeup/)

The same code can be used to solve this chall.

[solve.sage](https://github.com/CTF-STeam/ctf-writeups/blob/master/2020/ISITDTU%20Quals/Encrypt/solve.sage) [task3_sol.py](https://github.com/CTF-STeam/ctf-writeups/blob/master/2020/ISITDTU%20Quals/Encrypt/task3_sol_final.py)

Flag: `ISITDTU{NTRU_3ncrypti0n_alg0rithm_3asy!!!!!!!!}`

Original writeup (https://github.com/CTF-STeam/ctf-writeups/tree/master/2020/ISITDTU%20Quals/Encrypt).