Sha1() Encrypt & Decrypt

About Sha1 :

Sha-1 is a cryptographic function that takes as input a 2^64 bits maximum length message, and outputs a 160 bits hash, 40 caracters. Sha-1 is an improvement of Sha-0, it was created by the NSA, and improve cryptographic security by increasing the number of operations before a collision (theory says 2^63 operations), however Sha-1 is not considered as secure because 2^63 could be reach pretty easily. It was replaced by Sha-2 (224, 256, 384 and 512 bits), and more recently by Sha-3. Like Md5, Sha-1 is an unilateral function, to decrypt the plaintext behind a hash, you have to confront it to a online database. This website allows you to compare your Sha1 hashes and decrypt it if you're lucky, thanks to our efficient online database. This database contains 15,183,605,161 words, coming from all the wordlists I was able to find online. I then computed for days to enlarge the database and make it really unique, which will help you into Sha1 decryption.
About security, Sha-1 is not considered anymore as a secure hash type. If you still want to use it (and you should instead use Sha-2 functions), you should consider using a salt to make hackers life harder. A salt consist in a string you add to the user password before hashing it. This string could be a random sequence, a timestamp, or anything that will make the password harder to be found.