There are 3 main types of cryptography:

1) Symmetric cryptography - password based encryption that most everyone is familiar with. Not used at all in bitcoin.

2) Hashing algorithms - converting lots of data into irreversible gibberish. This is what bitcoin uses for mining and what ASICs are designed for.

3) Asymmetric cryptography/digital signatures - Totally different from symmetric or hashing and is what bitcoin uses for signing transactions and protecting coins and so on. An ASIC could be designed to brute force these, but the ones that are in development will not be capable of doing so.

It could be a stupid question, but would creating rainbow tables for MD5/LM/NTLM hashes be in the "Hashing algorithms" category?

Thx!