We are given the following Python code for encrypting the flag: from random import randint a = 288260533169915 p = 1007621497415251 FLAG = b'crypto{????????????????????}' def encrypt_flag(flag): ciphertext = [] plaintext = ''.join([bin(i)[2:].zfill(8) for i in flag]) print(plaintext) for b in plaintext: e = randint(1, p) n = pow(a, e, p) if b == '1': ciphertext.append(n) else: n = -n % p ciphertext.append(n) return ciphertext The way that the encryption works is that if it encounters a bit with value “1” in the binary representation of the plaintext (or the flag itself), then it appends $a^e \mod p$ to the ciphertext array, otherwise it appends $-a^e \mod p$.