MD5 hashing algorithm to encrypt principle, also known as hash algorithm hash algorithm.
Data structure of the computer science professional knowledge that there is a hash table.
For example, 10 divided by 3 is a remainder, 4 divided by 3 is also a remainder, but the remainder is a not know this number is which.
So md5 can not be decrypted.
Even if the encryption algorithm is designed this people do not know.
But how to verify your password is it? Because the same password encryption necessarily the same.
After you enter the password encryption to know your password is correct.
In other words, your password only you know.
Why is buttoned password can only be reset, the reason can not be retrieved.