What is the main purpose of triple-DES (3DES)?

• A. Increase effective key length and security against brute-force
• B. Faster than DES
• C. Provide hashing
• D. Provide authenticated encryption

Answer: (A)

Triple-DES aims to boost the strength of DES by running the algorithm three times with up to three keys, dramatically increasing the key length and making brute-force attacks far more difficult. DES uses a 56-bit key, which can be cracked with enough power; by encrypting with K1, decrypting with K2, and encrypting with K3, the effective key material becomes up to 168 bits, greatly enlarging the key space. This substantial increase in key length is the main benefit, trading off speed for security since 3DES must perform three DES operations for each block, making it much slower than DES. It does not provide hashing or built-in authentication; additional mechanisms would be needed for integrity or authenticity.