What statement about SHA-256 is supported by the concept of birthday attacks and hash output size?

• A. It is immune to birthday attacks
• B. It has the same collision space as MD5
• C. It cannot be used for integrity checks
• D. It has a larger collision space than weaker algorithms

Answer: (D)

Hash output size determines how hard it is to collide two inputs under a hash, and a birthday attack exploits that by showing collisions become likely after roughly 2^(n/2) attempts for an n-bit hash. With SHA-256’s 256-bit output, finding a collision sits around 2^128 evaluations, whereas a weaker algorithm like MD5 with 128-bit outputs requires about 2^64 evaluations. That means SHA-256 provides a much larger collision space, making collisions far harder to achieve compared to MD5. So the statement that it has a larger collision space than weaker algorithms is the best description. The other options contradict how birthday attacks scale with hash size and the practical use of hashes for integrity checks.