How do block ciphers differ from stream ciphers?

Block ciphers are designed to encrypt data in fixed-size blocks, which is one of the defining characteristics that sets them apart from stream ciphers. When data is processed by a block cipher, it takes a specified size of input (for example, 128 bits for AES) and encrypts that fixed group of bits at one time. This approach allows for various encryption modes that can help strengthen security, such as Cipher Block Chaining (CBC) or Counter (CTR) mode.

In contrast to block ciphers, stream ciphers work by encrypting data one bit or byte at a time, continuously streaming the data through the encryption algorithm. This is particularly useful for applications where data is generated in real-time or needs to be processed continuously, such as in network communications.

Understanding the nature of these two types of ciphers is essential for implementing strong encryption methods suited to specific use cases. The options that imply incorrect characteristics, such as equating block ciphers to the continuous encryption method of stream ciphers or making broad claims about security without context, do not accurately reflect the fundamental differences in operation and application between the two cipher types.