DHKE(script)

import random
import binascii

def Random_String_Generator(length):
    msg = ""

    while len(msg)!=length:
        i = random.randint(1,255)
        j = random.randint(1,255)

        s = (i*j)%128

        if s<33:
            s = random.randint(33,128)

        msg += str(chr(s))

    return(msg)

def xor(m,k):
    key = str(k)
    ct = ""
    for i in range(len(m)):
        ct += chr(ord(key[i%(len(key))])^ord(m[i]))
    return(binascii.hexlify(ct.encode()))

FLAG = "evlz{N0VV_Y0U_534_M3}ctf"

cnt = random.randint(40,60)
f = random.randint(20,30)

for i in range(cnt):
    alpha = random.randint(800000000,1000000000)
    p = random.randint(350000000000000,5500000000000000)
    print("\n\nalpha:",alpha)
    print("p:",p)

    A = int(input("\nGive me your A: "))
    b = random.randint(1,10)
    B = pow(alpha,b,p)
    print("Take my B:",B)

    KEY = pow(A,b,p)

    l = random.randint(20,30)
    m = Random_String_Generator(l)

    if i==f:
        ct = xor(FLAG,KEY)
    else:
        ct = xor(m,KEY)

    print("\nCiphertext:",ct)

    pt = input("\nPlaintext(encoded in hex): ")

    if binascii.unhexlify(pt).decode() == m:
        continue
    else:
        print("\noof")
        break

print("\nThanks")