how to compare sha1 encripted password in Java?

Question

Let say i have encripted SHA1 password like this

String pass = "f6ce584e7b4ff5253eed4a2ea2b44247";

and i want make condition like this :

 if (pass.equals("userinput")){
        System.out.println("success");
    }

please someone help me to make proper condition / function to compare those both value between user input and encripted password. Your help will be highly appreciated. thanks

Answer 1

SHA1 is a hash algorithm, which means that it is one-way. You can't get the original message after hashing it. Unlike encryption which is two-way (allows encryption and decryption).

This means that if you want to compare a hash, you don't try to get the original message. Instead, you hash the message-to-be-compared as well, then you perform the match:

So if the hashed pw is stored as:

String pass = "f6ce584e7b4ff5253eed4a2ea2b44247";

To match the subsequent input of the password, you do:

//check if hashed userInput is also "f6ce584e7b4ff5253eed4a2ea2b44247"
if(pass.equals(sha1(userInput))){          
    //do whatever
}

To implement a sha1() hash function, refer to: Java String to SHA1