Stream ciphers are a type of encryption method that encrypts data one bit or byte at a time. They use a key to generate a pseudo-random stream of bits, which is then combined with the plaintext data using a simple operation, typically the XOR operation. This allows for fast and efficient encryption, making stream ciphers suitable for applications where speed is crucial, such as in real-time communications. Unlike block ciphers, which encrypt fixed-size blocks of data, stream ciphers can handle data of varying lengths. This flexibility makes them ideal for scenarios like video streaming or voice over IP, where data is transmitted continuously. However, stream ciphers require careful key management to ensure security, as reusing keys can lead to vulnerabilities.