Could someone explain the differences between these two points? They seem identical to me.
> [The hash function] also should be second-preimage resistant: For a given message M1, it must be virtually impossible to find a second message M2 where M1 != M2 that produces the same hash hash(M1) == hash(M2).
> These functions should be also collision resistant: it must be virtually impossible to find two messages M1 and M2 where hash(M1) == hash(M2).
> [The hash function] also should be second-preimage resistant: For a given message M1, it must be virtually impossible to find a second message M2 where M1 != M2 that produces the same hash hash(M1) == hash(M2).
> These functions should be also collision resistant: it must be virtually impossible to find two messages M1 and M2 where hash(M1) == hash(M2).