What is the main difference between block ciphers and stream ciphers?

The main distinction between block ciphers and stream ciphers lies in how they process data. Block ciphers encrypt data in discrete, fixed-size blocks, which means that they take a specific number of bits (e.g., 128, 192, or 256 bits depending on the algorithm) and transform them into ciphertext. This approach requires that the entire block of data be prepared before encryption can occur, leading to a structured and thorough method of handling data.

In contrast, stream ciphers encrypt data as a continuous stream of bits. They process one bit or byte at a time, allowing for real-time encryption without the need for padding to fill a block. This can be particularly advantageous for applications that require low latency, such as real-time video or audio transmissions.

Understanding this framework clarifies why the selected answer accurately represents the core difference between block and stream ciphers. It highlights the operational characteristic that defines each cipher type, aiding in the comprehension of their respective applications and implications in the realm of cryptography.