Java simple class to compute MD5 hash

abstract

MD5 is a cryptographic message digest algorithm. MD5 hash considered to be one of the most widely-used used secure hashing functions, producing a 128-bit digest (32 hex numbers) from any data. While Java has built-in cryptographic checksum classes, it's quite uneasy to use them for a simple task -- calculate MD5 hash from string and return 32-byte hexadecimal representation.

compatible

Sun Java 1.4 or higher

We use MessageDigest class, first setting it to use MD5 algorithm, than feeding it with source data and getting byte array with hash value. To convert this array to hex-string we use our own method convertToHex.

Here is AeSimpleMD5 class, which single public static method MD5 returns hexadecimal string representation for MD5 hash of input argument:

 
import java.io.UnsupportedEncodingException; 
import java.security.MessageDigest; 
import java.security.NoSuchAlgorithmException; 
 
public class AeSimpleMD5 { 
 
    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 MD5(String text) 
    throws NoSuchAlgorithmException, UnsupportedEncodingException  { 
        MessageDigest md;
        md = MessageDigest.getInstance("MD5");
        byte[] md5hash = new byte[32];
        md.update(text.getBytes("iso-8859-1"), 0, text.length());
        md5hash = md.digest();
        return convertToHex(md5hash);
    } 
}

You may use this class directly calling this method

 
String MD5_ad1 = AeSimpleMD5.MD5("Java solutions class libraries");
String MD5_ad2 = AeSimpleMD5.MD5("Java Toolkits");

One more example, allows user to input string from console and prints MD5 hash

 
import java.io.BufferedReader; 
import java.io.IOException; 
import java.io.InputStreamReader; 
import java.io.UnsupportedEncodingException; 
import java.security.NoSuchAlgorithmException; 
 
public class Ex01 { 
 
    public static void main(String[] args) throws IOException { 
        BufferedReader userInput = new BufferedReader (new InputStreamReader(System.in));
 
        System.out.println("Enter string:");
        String rawString = userInput.readLine();
 
        try { 
            System.out.println("MD5 hash of string: " + AeSimpleMD5.MD5(rawString));
        } catch (NoSuchAlgorithmException e) { 
            // TODO Auto-generated catch block 
            e.printStackTrace();
        } catch (UnsupportedEncodingException e) { 
            // TODO Auto-generated catch block 
            e.printStackTrace();
        } 
    } 
}

warning

This class is suitable to calculate hash for small chunks of in-memory string data. To process large external files (like ISO images) you should use MessageDigest class directly

There may be difficulties while processing string data in encodings other than iso-8859-1.

tested

JDK 1.5