CRC32 has hash collisions for the inputs "plumless" and "buckeroo". What's the smallest data length for collisions in MD4, MD5, SHA-1, and the recently accepted SHA-3 (Keccak)? We know that lim_len n->infty p(collision) = 1.0, but I'm curious how large your data has to be before a particular hash algorithm actually experiences a collisions.
Can MD4 collide on blocks less than 100 byes? 1000? 10^10? 10^20? ...