Explanation of pseudo-collisions

Question

Give a brief explanation of pseudo-collisions.

Answer 1

Pseudo-collisions are collisions for the compression function which lies at the heart of the iterative hash function. While collisions for compression function of the hash function may be useful in constructing collisions for hash function itself, this is not normally the case. While pseudo-collisions may be viewed as the unfortunate property of the hash function, a pseudo-collision is not correspondent to the collision, and the hash function can silent be secure.