What type of encryption algorithm is RC4?

RC4 is a stream cipher, which means that it encrypts plaintext one byte or one bit at a time, rather than processing data in fixed-size blocks as block ciphers do. Stream ciphers are particularly useful for scenarios where data is transmitted in a continuous stream, allowing for more efficient and quicker encryption and decryption processes.

As a stream cipher, RC4 generates a pseudorandom stream of bits called the keystream, which is then XORed with the plaintext to produce ciphertext. This method enables secure communication by allowing the data to be encrypted on-the-fly without needing to wait for large blocks of data to accumulate.

In contrast, block ciphers operate on fixed-size blocks of data (such as 128 or 256 bits) and require padding when the data doesn't perfectly fit the block size. Modes of operation refer to specific methods of using block ciphers to achieve various implementations, while hashing algorithms perform a completely different function by converting data into a fixed-size hash value rather than encryption. Thus, RC4's classification as a stream cipher makes it unique and distinct from these other types of encryption algorithms.