Stream cipher

What is Stream Cipher?
A stream cipher is an encryption method in which a pseudo-random stream of digits is combined with plaintext digits. This pseudo-random digit stream is applied to each binary digit, one bit each. This encryption method uses an infinite number of pseudo-random digits per key. Stream cipher is also known as state cipher.
A stream cipher encrypts any length of plain text, one bit at a time, with an algorithm that uses a key. In order for this form of encryption to remain secure, its pseudo-random digits should not be predictable and the key should never be used more than once.

The pseudo-random digit digits are generated by a number of random seed values using digital shift registers. The encryption of each digit depends on the current state of the cipher and guarantees the name state encryption. RC4 is a popular stream cipher that is widely used in software.