Md5() Encrypt & Decrypt

About Md5 :

Md5 (Message Digest 5) is a cryptographic function that allows you to make a 128-bits (32 caracters) "hash" from any string taken as input, no matter the length (up to 2^64 bits). This function is irreversible, you can't obtain the plaintext only from the hash. The only way to decrypt your hash is to compare it with a database using our online decrypter. Here we have a 10.000.000.000+ md5 hash database to help you with decryption. One should know that md5, although it's very used and common, shouldn't be use to encrypt critical data, since it's not secure anymore (collisions were found, and decrypt is becoming more and more easy). If you are building a new website, Sha-256, 512, or other kinds of encryption (with salt) would be better than md5, or even sha-1. Our decrypter database is coming from all the wordlist I was able to find on the internet. I then sorted them, and enlarge the final wordlist by creating a script that multiplicated the list to finally lend to a unique and pertinent wordlist.

Md5 is no longer considered as a secure way to store passwords. In 2004, chinese scientists found a complete collision on md5. Since that date, collisions became easier and easier due to the increasing calculation power. It is now possible to find a md5 collision in a few minutes. If you are interested into md5 collisions and want to know more, you can check this link. It is now better to use hash functions such as Sha256, 512, bcrypt, scrypt, whirlpool for instance.
If you still want to use md5 to store passwords on your website, good thing would be to use a "salt" to make the hash more difficult to crack via bruteforce and rainbow tables. A salt is simply a caracters string that you add to an user password to make it less breakable. For instance, say we are using the password "password" (good idea). It will be obviously really easy to break. Then before storing this password in your database, you just concatenate a random string (generated with a php function for instance) such as a~/!c^12/*bn@( for example. That would make the password look like a~/!c^12/*bn@(password, which is obviously really harder to crack. Please note that it is preferable to use random generated strings as salt, if you just use the same string for each password it will be far too easy to break. You could also be creative and split the salt in two, then add a part at the beginning of the password and the other part at the end. Or for instance hash the salt before you concatenate it, everything is good to complexify your password before storing it.

By the way, if you're looking for a good way to remember very hard-to-break passwords, as a user, you could use sentences instead of a word. For instance illrememberthispasswordthatsforsure, will be really hard to break through bruteforce and rainbow tables. And that'll be even harder if you add uppercase and some numbers such as Hiimjohnandiwasbornin1980 for instance. It's easy to remember and hard to crack.