Java MD5 for Linux

Question

Hi @all
I'm trying to write a method in Java, that receives a String and should return the MD5 hash of this String.
This hash should be usable to change the password of a user in linux with usermod -p "hash" user.
Here is my method:
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<BEGIN>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
public String createMD5HashCode(String text) throws NoSuchAlgorithmException, NoSuchProviderException {
String result = text;
if (text != null) {
StringBuffer code = new StringBuffer(); //the hash code
String plain = text;
byte bytes[] = plain.getBytes();
MessageDigest messageDigest = MessageDigest.getInstance("MD5", "SUN");
messageDigest.update(bytes);
byte digest[] = messageDigest.digest(bytes); //create code
System.out.println(digest.length);
for (int i = 0; i < digest.length; ++i) {
code.append(Integer.toHexString(0x0100 + (digest & 0x00FF)).substring(1));
result = code.toString();
return result;
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And if i try to change the password with "usermod -p 'returned hash' user", it works, but i can't login anymore :-(
Are there any proposals?
Thanks for your help in advance.
Regards
daenu

Answer 1

public String createMD5HashCode(String text) throws
NoSuchAlgorithmException, NoSuchProviderException {
String result = text;
if (text != null) {
StringBuffer code = new StringBuffer(); //the hash
code
String plain = text;
byte bytes[] = plain.getBytes();You should realy specify the encoding here eg plain.getBytes("ASCII")
MessageDigest messageDigest =
MessageDigest.getInstance("MD5", "SUN");
messageDigest.update(bytes);This will add 'bytes' to the digest.
>
byte digest[] = messageDigest.digest(bytes); //createand this will add them again! You don't need the update.
code
System.out.println(digest.length);
for (int i = 0; i < digest.length; ++i) {
code.append(Integer.toHexString(0x0100 + (digest &
0x00FF)).substring(1));Very interesting! It took me some time to work out what this was doing!
result = code.toString();
return result;