# ROR Writeup
### zer0pts CTF 2020 - crypto 260
> LOL
#### Observations
Plain RSA cryptosystem given. I was given only set of ciphertexts, which were generated by RORing flag. `2` is factor of public modulus `N`, so applying modular operation does not change the parity of rotated plaintext. Every bit of plaintext can be recovered by just observing least significant bits of ciphertexts.
#### Get flag
Concat every LSBs of ciphertext and get flag:
```zer0pts{0h_1t_l34ks_th3_l34st_s1gn1f1c4nt_b1t}```
Exploit code: [solve.py](solve.py)