algy.py

# Python 2.7
from Crypto.Util.number import *

f=file('flag','r')
theflag = f.read()
f.close()

p=257
key = getRandomRange(3,p-3)

def encrypt(pt, key, p):
    bytearray=[]
    for ltr in pt:
        bytearray.append(key*inverse(ord(ltr), p) % p)
    return "".join(map(chr, bytearray))

ct = encrypt(theflag.strip(), key, p)

f=file('ciphertext','w')
f.write(ct.encode('hex'))
f.close()

ciphertext

d2dcd257d1a90ea0a067a2dbcfa246a2dbcfe7bca2db04a2a0b3d2a2cf0e6b4bc787cf8d3ea23e87048ed0a052