RC4 is an example of which type of encryption?

RC4 is a widely recognized example of a stream cipher. Stream ciphers encrypt data by processing individual bits or bytes of plaintext data sequentially, allowing for real-time encryption and decryption as the data is being transmitted. This characteristic makes stream ciphers particularly effective for scenarios where data is being processed in a continuous flow, such as network communications.

RC4 specifically employs a varying key length and utilizes a key scheduling algorithm to initialize its internal state, which is then used to produce a keystream that is combined with the plaintext to produce the ciphertext. The simplicity of this approach, along with its performance efficiency, contributed to its extensive use in various protocols, despite known vulnerabilities that have prompted security professionals to move towards more secure alternatives.

The other categories listed—block ciphers, mode of operation, and hashing—represent different methods of managing encryption and data integrity but do not describe the operational mechanism of RC4. Block ciphers operate on fixed-size blocks of data, while modes of operation dictate how block ciphers can be applied to data of varying sizes. Hashing, on the other hand, is a one-way function designed to produce a unique hash value from input data, rather than providing a reversible encryption method like stream ciphers.