# What does the minimal number of round of “nr” use Keccak to avoid “collision attack”?

What does the minimal number of round of "nr" use Keccak to avoid collision attack?

$$nr = 12+2L$$

• Welcome to Cryptography. I've edited your question. Please check, there are still some points. The Collision attack is inevitable. You should give a probability bound to achieve. See the birthday attack or Sweet32 – kelalaka Mar 10 at 14:33
• @kelalaka How is sweet32 relevant? There are standard costs widely understood to be unachievable; when a collision attack on a widely used unkeyed hash function at a reasonable length is achievable once it is usually bad news for everyone, so there's not much sense in asking about specific probability bounds in this context. – Squeamish Ossifrage Mar 10 at 15:08