Future Business Leaders of America (FBLA) Cybersecurity Practice Test

Which encryption standard uses a block size of 64 bits?

1. AES

2. DES

3. Twofish

4. Triple DES

The correct answer is: DES

The correct answer is based on the specifications of the Data Encryption Standard (DES). DES utilizes a block size of 64 bits, which means that it processes data in chunks of 64 bits at a time. This block size is a significant characteristic of the DES algorithm, initially adopted in the early 1970s. In contrast, other encryption standards mentioned have different block sizes. Advanced Encryption Standard (AES), for example, uses a block size of 128 bits regardless of key length. Twofish also employs a block size of 128 bits, as does Triple DES, which essentially applies the DES algorithm three times for added security but still retains the same 64-bit block size as its base (while primarily functioning with a 128-bit effective block size due to the three iterations). Understanding the block size helps in evaluating the strength and efficiency of encryption methods. DES, with its smaller block size, was deemed less secure as computing power increased, leading to its eventual replacement by stronger standards. Thus, DES's 64-bit block size is a key defining feature, making it the correct answer in identifying which of the listed options uses that specific block size.