DES uses block encryption.

• A. True
• B. False
• C. Not used
• D. Both

Answer: (A)

DES is a block cipher. It encrypts data in fixed-size blocks of 64 bits, using a 56-bit key through 16 rounds of a Feistel network to produce 64-bit ciphertext. Because it works on blocks, longer messages are handled by applying padding and a mode of operation (such as CBC or ECB), rather than encrypting bit-by-bit. A stream cipher, in contrast, would generate a keystream and encrypt data as a stream rather than in fixed blocks. So the statement is correct. The other options don’t fit because DES is not a stream cipher, and it’s not something you’d call “not used” or “both.”