2. After your explanation in part 1), Barney agrees to use SHA-2 for hashing. However, to save space he proposes to only use the first 128 bits to create a 128 bit hash. He argues that since 128 bit encryption keys are secure, a 128 bit hash should also be secure. Explain what kind of attack a 128 bit hash would be vulnerable to, and why.

Preimage attack and collision attacks.

Explanation:

When SHA-2 hashing is used with only 128 bit hash, It usually makes the system vulnerable to attack.

Main disadvantage in case of truncated SHA is that there exist no reduction proofs to the original hash function. It implies that the truncated version is thus is very much resistant to preimage attack and collision attacks.

Collision resistant system does not always implies to collision free. If 128 bit hash is used for say any file greater than 16 bytes, then atleast two collision occurs. It can occur anytime in the beginning in starting one or two documents at any later stage. It will lead to a situation where one will not be able to write second or will ultimately overwrite the first one.

well cos like a ds it doesn't really die out, unlike for example, fifa, they always come out with a new version, so lets say your fifa 18 is charging you to update the teams and stuff, so, if messi were to go to real madrid (never gonna happen) it would switch messi to the other team, until the owners of fifa come out with fifa 19, then the game would eventually stop updating, and back to the ds, it doesn't really stop working after sometime because there's lots of things that it could be used for, and idk if u know what i'm saying, but long story short, samsung, represents the ds, if they still work, and people love them but not the new version, the old version still works, so they don't really force people to buy new phones, get me?

you paid for the subscription lol