CompTIA
SY0-301 · Question #737
SY0-301 Question #737: Real Exam Question with Answer & Explanation
The correct answer is B: DES. DES and 3DES are symmetric block ciphers that both operate on 64-bit block sizes, distinguishing them from AES which uses a 128-bit block size.
Question
Which of the following are restricted to 64-bit block sizes? (Select TWO).
Options
- APGP
- BDES
- CAES256
- DRSA
- E3DES
- FAES
Explanation
DES and 3DES are symmetric block ciphers that both operate on 64-bit block sizes, distinguishing them from AES which uses a 128-bit block size.
Common mistakes.
- A. PGP (Pretty Good Privacy) is an encryption program and standard, not a block cipher with a defined block size.
- C. AES256 refers to AES with a 256-bit key; AES uses a 128-bit block size regardless of key length.
- D. RSA is an asymmetric (public-key) algorithm that does not use fixed block sizes in the same way as symmetric block ciphers.
- F. AES (Advanced Encryption Standard) uses a 128-bit block size for all key lengths (128, 192, or 256 bits).
Concept tested. DES and 3DES 64-bit block size characteristic
Reference. https://csrc.nist.gov/publications/detail/fips/46/3/archive/1999-10-25
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