RC4-Fix.py

import numpy as np
def KSA(key):
	key_length = len(key)
	S = list(range(256))
	j = 0
	for i in range(256):
		j= (j + S[i] + key[i % key_length]) % 256
		S[i] , S[j] = S[j], S[i]
	return S

def PRGA(S, n):
	i=0
	j=0
	key=[]
	while n>0:
		n=n-1
		i = (i + 1) % 256
		j = (j + S[i]) % 256
		S[i], S[j] = S[j], S[i]
		K = S[(S[i] + S[j]) % 256]
		key.append(K)
	return key

key = "1337sec"
plaintext = "DarkArmywillcomeforyou"

def preparing_key_array(s):
	return [ord(c) for c in s]

key = preparing_key_array(key)

S = KSA(key)
keystream = np.array(PRGA(S, len(plaintext)))
print(keystream)
plaintext = np.array([ord(i) for i in plaintext])
cipher = keystream ^ plaintext
print(cipher.astype(np.uint8).data.hex())
print ([chr(c) for c in cipher])