In cryptography , a stream cipher is a symmetric key cipher where plaintext bits are combined with a pseudorandom cipher bit stream -LRB- keystream -RRB- , typically by an exclusive-or -LRB- xor -RRB- operation .

In cryptography , a stream cipher is a symmetric key cipher where plaintext bits are combined with a pseudorandom cipher bit stream -LRB- keystream -RRB- using an exclusive-or -LRB- xor -RRB- operation .
