What is the main advantage of a stream cipher compared to a block cipher?

The primary advantage of a stream cipher lies in its ability to encrypt data in a continuous flow, which generally allows for faster processing speeds compared to block ciphers that handle fixed-size blocks of data. Stream ciphers can efficiently encrypt data one bit or byte at a time, making them ideal for situations where low latency is crucial, such as in real-time communications.

Additionally, stream ciphers often use keys that can be employed only once during the encryption process, a practice known as the one-time pad. This method enhances security by ensuring that each encryption is independent. As a result, this approach significantly reduces the risk of attacks that exploit key reuse.

In contrast, while block ciphers are also secure and widely utilized, they may become less efficient when handling data streams or varying input sizes, particularly in scenarios requiring immediate data processing. Therefore, the speed and application of reusable keys, specifically in the context of real-time data, are what distinctly highlight the advantages of stream ciphers.