Question

Is MD5 hash function is indistinguishable and non-malleable? Explain it.

Answer 1

Yes, Message Digest 5 (MD5) hash function is indistinguishable and non-malleable. The two desirable properties of a hash function are:
1) Pseudo-random: The function behaves indistinguishably from a random oracle.
2) Non-malleability: With J(x), it is difficult for generating J(f(x)) for any function f. Malleability is the expander hash design's inherent property. Malleability properties show negative implications for certain hash functions applications' security however, for Cayley hashes though, they give rise to efficient parallel computation algorithms.

MD5 cryptographic hash function should be computationally infeasible to find two distinct messages hashing to the same value however, MD5 fails catastrophically in this regard, unable to meet this requirement.

Thus, a hash function should be indistinguishable from a pseudorandom function and unforgeable or non-malleable when used as a MAC.