Decrypt a password of SecureSHA1 Hashing in Java?

Question

I have encrypted my password(Password1234$) using SecureSHA1and got the following

Output: SHA1 hash for Password1234$ is 12a00057ae853a05601d5fafb7bc8141c37eaabe.

I want to write a Decryption Method for the same so that if i pass my encrypted string 12a00057ae853a05601d5fafb7bc8141c37eaabe. i need to get my password Password1234$

Below is my code which i used to Encrypt the Password.

SecureSHA1.java

import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class SecureSHA1 {
    private static String convertToHex(byte[] data) { 
        StringBuffer buf = new StringBuffer();
        for (int i = 0; i < data.length; i++) { 
            int halfbyte = (data[i] >>> 4) & 0x0F;
            int two_halfs = 0;
            do { 
                if ((0 <= halfbyte) && (halfbyte <= 9)) 
                    buf.append((char) ('0' + halfbyte));
                else 
                    buf.append((char) ('a' + (halfbyte - 10)));
                halfbyte = data[i] & 0x0F;
            } while(two_halfs++ < 1);
        } 
        return buf.toString();
    }


    public static String getSHA1(String text) 
                throws NoSuchAlgorithmException, UnsupportedEncodingException  { 
        MessageDigest md;
        md = MessageDigest.getInstance("SHA-1");
        byte[] sha1hash = new byte[40];
        md.update(text.getBytes("iso-8859-1"), 0, text.length());
        sha1hash = md.digest();
        return convertToHex(sha1hash);
    } 

    public static void main(String args[]){
        try {
            String s = "Password1234$";
            String sha1S = getSHA1(s);
            System.out.print("SHA1 hash for "+ s+ " is "+ sha1S);
        } catch (Exception e) {
            System.out.println(e);
        }

    }
}

A one way hash function is not encryption, and SHA1 is a one way hash. — Elliott Frisch, Nov 25 '15 at 06:11
@ElliottFrisch So, i cant get my password back once it was hashed with SHA1. — 09Q71AO534, Nov 25 '15 at 06:13
Exactly. See http://stackoverflow.com/questions/15521372/is-it-possible-to-encrypt-and-then-decrypt-a-string-using-md5-and-java (refers to MD5 but the concept is the same) — Andreas Fester, Nov 25 '15 at 06:15

score 4 · Answer 1 · answered Nov 25 '15 at 06:15

4

There is a big difference between encryption and hashing. Encryption is designed so you encode and decode something using a key.

Hashing is specifically designed to be a one-way calculation. You can't get the input from the output, except by brute force.

SHA1 is a hashing algorithm.

answered Nov 25 '15 at 06:15

Thomas Stets

3,015
4
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Do we have any Brute Force Algorithm implemented. – 09Q71AO534 Nov 25 '15 at 06:26
A brute force approach would be to simple try to hash any possible input value until you create the same hash. If the input is short, like passwords, a list of pre-computed hashes helps. That's called a rainbow table. That is also a reason why you don't just hash password, but use a "salt". (google for "rainbow table" and "password salt" to learn more) – Thomas Stets Nov 25 '15 at 06:35
Thanks for the suggestions ;) – 09Q71AO534 Nov 25 '15 at 08:47

score 1 · Answer 2 · edited May 23 '17 at 12:15

1

The answer is that you cannot reverse an SHA1 hash!

See this post for further details: Is it possible to reverse a sha1?

edited May 23 '17 at 12:15

Community

1
1

answered Nov 25 '15 at 06:16

Imran Ahmed

790
1
9
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Decrypt a password of SecureSHA1 Hashing in Java?

2 Answers2