RC4, also known as ARC4 or ARCFOUR, is a stream cipher.
Python implementation
def rc4(key):
key_len = len(key)
s = list(range(256))
j = 0
for i in range(256):
i &= 0xFF
j = (j + s[i] + key[i % key_len]) & 0xFF
# Swap s[i] and s[j]
tmp = s[i]
s[i] = s[j]
s[j] = tmp
i = 0
j = 0
while True:
i = (i + 1) & 0xFF
j = (j + s[i]) & 0xFF
# Swap s[i] and s[j]
tmp = s[i]
s[i] = s[j]
s[j] = tmp
yield s[(s[i] + s[j]) & 0xFF]
import itertools
keystream = rc4(b"Secret")
buf = bytes(itertools.islice(keystream, 16))
print(buf.hex()) # def rc4(key):
key_len = len(key)
s = list(range(256))
j = 0
for i in range(256):
i &= 0xFF
j = (j + s[i] + key[i % key_len]) & 0xFF
# Swap s[i] and s[j]
tmp = s[i]
s[i] = s[j]
s[j] = tmp
i = 0
j = 0
while True:
i = (i + 1) & 0xFF
j = (j + s[i]) & 0xFF
# Swap s[i] and s[j]
tmp = s[i]
s[i] = s[j]
s[j] = tmp
yield s[(s[i] + s[j]) & 0xFF]
import itertools
keystream = rc4(b"Secret")
buf = bytes(itertools.islice(keystream, 16))
print(buf.hex())
# Prints 04d46b053ca87b594172302aec9bb992
