User Code: Make an SHA Fingerprint from a String

It's possible, in an applet, that this code won't work for some Netscape Navigator versions, because they don't have the MessageDigest class included (perhaps this only concerns European versions, because of some export restrictions to cryptographic code).

In that case, as far as I know, the only way to implement the SHA is to follow Steve Reid's originial C++ code step by step. But there also exist some Java translations on the Net.

How It Works

You just call makeSHA("Hello World!"), and you'll get back a string consisting of the hex-view of the encoded bytes.

import java.io.*;
import java.lang.*;
import java.security.*;
import java.util.*;

public class mysha {

 public static String toHexString(byte b)
   {
     int value = (b & 0x7F) + (b < 0 ? 128 : 0);
     String ret = (value < 16 ? "0" : "");
     ret += Integer.toHexString(value).toUpperCase();
     return ret;
   }

 public static String makeSHA(String inputstring) {
 String outputstring="";
 try
 {
  // Objekt mit SHA" holen => initialize SHA object
  MessageDigest md = MessageDigest.getInstance("SHA");

  byte[] myText = inputstring.getBytes();
  md.update(myText);
  
  // Berechnen => Calculate

  byte[] result = md.digest();
  // Ausgeben => Output
    for (int i = 0; i < result.length; ++i) {
   outputstring=outputstring+toHexString(result[i]);
  }
  
  }
  catch ( Exception e) {
  System.out.println("Error"+e);
  }
  return outputstring;

 }


 public static void main(String arguments[]) {
  // runs test-vector "abc"
  System.out.println(makeSHA("abc"));

 }


}

About the Author

Andreas Brandmaier is a student at the University of Munich, working with statistical databases using Perl and Java.

Java users are encouraged to submit samples of useful code for publication in the pages of Gamelan. Send your files and comments to editor@developer.com for consideration. Thank you.

This article was originally published on December 19, 2001