Bob is worried that the program someone gave him at DEFCON h

Bob is worried that the program someone gave him at DEFCON has been altered from the original. Which of the following is a valid technique that Bob can use to verify its authenticity?

A. Run AES against the program.

B. Compare the size and date with the version found on the developer’s website.

C. Run an MD5sum and check against MD5sum from developer sites.

D. Calculate a digital signature.

Solution

C. Running an MD5sum would be the best way for Bob to verify the program. MD5sum is a hashing algorithm. Answer A is incorrect because AES is a symmetric algorithm and will not help Bob verify the program. Answer B is incorrect because the size and date might match the information found on the developer’s website, but the program might have still been altered. Answer D is incorrect because a digital signature will not verify the integrity of the program