Wouldn't MD5 encrypting be reverse engineering by computing once and for all the hash of every string?

I was reading about MD5 encrypting with java. And I was wondering how it can be safe while you can just compute once and for all the hash of every possible string. That would sure take a bit of time but once it's done you ca开发者_运维知识库n just store all the couples inside a database table, and search for any hashcode in this table quite fast... right?

What am i missing?

Thanks in advance.

MD5 generates 2^128 possible values, so you need at least 2^128 strings hashed for complete coverage. Hashing 2^32 strings every second (which is A LOT) you will need 79228162514264337593543950336 seconds, which is 2512308552583217199186 years.

Personally, I do not expect to last so long. And it's quite possible that the universe will not too.