Originally posted by psyno
I'm brand new to Linux but I gather that md5 is used for more than just checksums. I don't know how yet, but I think it is useful for password encryption and the like.
MD5 is not an encryption mechanism. It produces a "message digest" or checksum that can be used to verify data integrity. I realize that "MD5 passwords" are common, but they are not encrypted. What is actually stored or compared is the checksum of the password. Theorectically, only the real password will produce the correct MD5 checksum.
If you look at things like SSL, you'll notice that during the connection negotiation, things like encryption cipher (DES, 3DES, IDEA) and the checksum (MD5, SHA) are chosen during the initial handshake.