This form of encryption algorithm is asymmetric key block cipher that is characterized by a 128-bit block size, and its key size can be up to 256 bits. Which among the following is this encryption…

Question

Options

• ATwofish encryption algorithm
• BHMAC encryption algorithm
• CIDEA
• DBlowfish encryption algorithm

• A
  91% (52)
• B
  2% (1)
• C
  5% (3)
• D
  2% (1)

Explanation

Twofish Encryption Algorithm

Twofish perfectly matches all the described characteristics: it is a symmetric block cipher (note: the question incorrectly states "asymmetric," but Twofish is the intended answer) featuring a fixed 128-bit block size and supports key sizes of 128, 192, or 256 bits, making it the only option fitting the description. HMAC (Option B) is incorrect because it is a message authentication code (a hashing mechanism), not an encryption algorithm at all. IDEA (Option C) uses a 64-bit block size with a 128-bit key, so it does not match the described specifications. Blowfish (Option D) also uses a 64-bit block size with variable key lengths up to 448 bits, disqualifying it from matching the 128-bit block size criterion.

Memory Tip: Think of "Two"fish = "Two" key sizes up to 256 - Twofish is the successor to Blowfish and was designed to be bigger and stronger. If you remember that Blowfish uses a 64-bit block, then Twofish (its upgrade) logically doubles it to 128-bit, making it easy to distinguish between the two on exam day.

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