How we find a plaintext in rainbow table after delete all chain except first and end of chain

Question

I started to learn rainbow tables and I have a question : How we can find a plaintext of hash if we delete all chain except first and end plaintext If It is wrong and we don't delete chain , why we don't use a normal pre-computing hashing table because it will use the same space , why we specifically use rainbow tables.

Answer 1

I had a bit of trouble understanding what you mean. I'll try my best to answer your question though.

A rainbow table is just a table where every row contains a plaintext and the corresponding hash. You generate such table for a big number of plaintexts, but at some point you reach a limit of space, so usually your plaintexts are not longer than 9 characters. All the present day password hashing mechanisms are rainbow table proof. They use salt to artificially make the passwords longer. So rainbow tables are more or less dead at the moment.

What you still can do is to take salt out of the hash and for the given salt value generate a whole bunch of digests. So you will have a kind of a rainbow table made for one salt dimension. Not so efficient any more, but you might get lucky.