DES uses keys of what size?

Data Encryption Standard (DES) utilizes a key size of 56 bits. This size was determined when DES was originally designed in the 1970s and has since been a defining characteristic of the algorithm. The 56-bit key allows for a significant number of possible keys, specifically 2^56, which provides a baseline level of security for that time. However, it is important to note that due to advancements in computational power and cryptographic techniques, DES has become increasingly vulnerable to brute-force attacks.

The other options represent key sizes associated with different encryption algorithms. For example, 128 bits and 192 bits are commonly associated with the Advanced Encryption Standard (AES), which was developed as a more secure alternative to DES. The 64-bit option is also misleading since DES processes data in 64-bit blocks but uses a 56-bit key for encryption. Thus, choosing 56 bits correctly identifies the key size specifically used in DES.