see http://mindprod.com/jgloss/digest.html

--
Canadian Mind Products, Roedy Green.
Coaching, problem solving, economical contract programming.
See http://mindprod.com/jgloss/jgloss.html for The Java Glossary.

  This is strange, because message digests do not have keys.

  You need something like this:

import java.security.MessageDigest;

MessageDigest mesdig;
try {
   mesdig=MessageDigest.getInstance("MD5");
} catch (NoSuchAlgorithmException a) {
   System.err.println("No MD5: "+a);
   return;
}

// mesdig is now a fresh MD5 instance, ready for data.
mesdig.update((byte)'a');
mesdig.update((byte)'b');
mesdig.update((byte)'c');
mesdig.update((byte)'\n');

// That's all the data. Now let it calculate the hash.
byte[] result=mesdig.digest();

// Print the result in hex.
for (int jj=0; jj<result.length; ++jj) {
   System.out.print("0123456789ABCDEF".charAt((result[jj]>>4) & 0x0F));
   System.out.print("0123456789ABCDEF".charAt(result[jj] & 0x0F));
}
System.out.println();

  This prints out 0BEE89B07A248E27C83FC3D5951213C1, which agrees with
the output of the Linux md5sum command:
   [maa@orion maa]$ echo abc|md5sum
   0bee89b07a248e27c83fc3d5951213c1  -

--Mike Amling