3DES Algorithm: Features and Security | Cisco Exam 400-251

3DES Algorithm

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Which statement about the 3DES algorithm is true?



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A. B. C. D. E.


The correct statement about the 3DES algorithm is:

C. The 3DES algorithm is a block cipher.


The 3DES algorithm is a symmetric-key block cipher that encrypts data in blocks of 64 bits. It is a variant of the original Data Encryption Standard (DES) algorithm, which was considered secure in the 1970s but is now vulnerable to brute-force attacks due to its small key size.

To improve the security of DES, the 3DES algorithm was introduced in the late 1990s. It uses a key size of 168 bits, which is created by applying the DES algorithm three times with different keys. This is known as triple encryption.

The 3DES algorithm uses the same key for encryption and decryption, which makes it a symmetric-key algorithm. The use of triple encryption with different keys provides a high level of security and makes 3DES more resistant to brute-force attacks than DES. However, the use of three keys makes 3DES slower than DES.

Therefore, options A and E are incorrect. Option B is incorrect because the 3DES algorithm uses a symmetric-key pair, not a public-private key pair. Finally, option D is incorrect because the 3DES algorithm uses a key length of 168 bits, not 112 bits.