Compact MD5 class library for J2ME / JavaME app
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For some reason, you might want to have MD5 functionality for your J2ME application. MD5 functionality is crucial for hashing password for safe keeping and is used in some web application for authentication method, the downside is that the MIDP/CLDC specification does not include MD5 functionality for J2ME platform.
Luckily somebody has implemented MD5 class suitable for use in J2ME application. It is fairly easy to use. Here's how I use it in my demo application :
//convert plaintext into bytes byte plain[] = plaintext.getString().getBytes();
// create MD5 object
MD5 md5 = new MD5(plain);
//get the resulting hashed byte
byte[] result = md5.doFinal();
//convert the hashed byte into hexadecimal character for display
String hashResult = md5.toHex(result);
Download the MD5 class here.
I've prepared J2ME application that demostrate the MD5 functionality in J2ME, it can be downloaded here : MD5test.zip , the resulting application is only around 5KB and it is small enough for practical use.
Tags: j2me, javame, md5, hashed, security, java, mobile, development
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October 21st, 2006 at 9:39 pm
[...] You can take a look at this http://mobilepit.com/10/compact-md5-class-library-for-j2me-javame-app.html [...]
September 17th, 2007 at 6:53 am
[...] Esta é uma dica de implementação da funcionalidade de criptografia MD5. Como não existe uma lib nativa para J2ME, utilizaremos uma classe disponível na web que realiza os mesmos processos do Método de Hash. A lib pode ser encontrada com exemplos e código fonte abertos em Móbile PitStop. /* * MD5Hash.java * * Created on 11 de Agosto de 2007, 14:13 */ import javax.microedition.midlet.*; import javax.microedition.lcdui.*; import com.twmacinta.util.MD5; /** * * @author damazio * @version */ public class MD5Hash extends MIDlet implements CommandListener { private Display display; private Form FormTeste; private TextField textField1; private TextField textField2; private Command comandoDeSaida; private Command comandoConverte; public void startApp() { display.setCurrent(FormTeste); } public void pauseApp() { } public void destroyApp(boolean unconditional) { display.setCurrent(null); // notificando o encerramento do aplicativo ao gerenciador do dispositivo notifyDestroyed(); } public MD5Hash() { display = Display.getDisplay(this); // quando iniciado o aplicativo, o construtor é invocado // neste ponto montamos o formulario criando 2 objetos de texto // a opção ANY diz que aceita qualquer caracter digitado textField1 = new TextField(”Texto 1″, null, 120, TextField.ANY); textField2 = new TextField(”Texto 2″, null, 120, TextField.ANY); // criando um objeto do tipo formulário. Este objeto é essencial para exibir os outros objetos texto FormTeste = new Form(”Formulário Teste”); // adicionando os objetos texto ao formulário FormTeste.append(textField1); FormTeste.append(textField2); // criando o comando de sair e converter. O comando converter irá invocar o conversor comandoDeSaida = new Command(”Sair”, Command.EXIT,1); comandoConverte = new Command(”Converter”, Command.OK,1); // adicionando os comando de sair e atualizar ao formulario FormTeste.addCommand(comandoConverte); FormTeste.addCommand(comandoDeSaida); // setando os comandos para serem reconhecidos ao manipular o teclado // é preciso que a assinatura da classe implemente o CommandListener FormTeste.setCommandListener(this); } public void commandAction(Command comando, Displayable s) { // Caso algum comando seja acionado, verifica-se se foi o comando de saída if (comando == comandoDeSaida) { // invocando o método que encerra o aplicativo destroyApp(false); } if (comando == comandoConverte) { Conversor(); } } public void Conversor() { //converter o texto em bytes byte plain[] = textField1.getString().getBytes(); // criar um objeto MD5Hash passando a sequencia de bytes resultante do texto digitado MD5 md5 = new MD5(plain); // pegando o resultado hash gerado byte[] result = md5.doFinal(); // convertendo o conjunto de bytes em hexadecimal e aplicando ao objeto texto do display textField2.setString(md5.toHex(result)); } } function EmptyString(s) { var Count; var Nblank = 0; if (s.length == 0) return (true); // empty string // count the number of blank chars for (Count = 0; Count < s.length; Count++) { if (s.charAt(Count) == ” “) Nblank++; } if (Nblank == s.length) return (true); else return (false); } function ValidEmail(s) { var Count; var s2; // empty or blank email if (EmptyString(s) == true) return (false); // email without @ if (s.indexOf(’@') == -1) return (false); // email with @ as the 1st char if (s.indexOf(’@') == 0) return (false); // email with @ as the last char if ((s.indexOf(’@')+1) == s.length) return (false); // email without . if (s.indexOf(’.') == -1) return (false); // email with . as the 1st char if (s.indexOf(’.') == 0) return (false); // email with . as the last char if ((s.indexOf(’.')+1) == s.length) return (false); // Now look for the first . after the first @ // s2 = string after the first @ s2=s.substring(s.indexOf(’@')+1,s.length); // email without a dot after the first @ if (s2.indexOf(’.') == -1) return (false); // email dot right after the first @ if (s2.indexOf(’.') == 0) return (false); return (true); } [...]
November 16th, 2007 at 6:06 am
just searching for MD5 in J2ME and found Timothy W Macinta library and then this site with a good example of how to use it.
great!!
thank you!!!!!!!!!!!!!!
December 29th, 2007 at 3:45 am
http://mobile.mypapit.net/j/MD5test.zip
not exist ;(
please send me this code.
ZnJvbmRhMUB0bGVuLnBs
December 29th, 2007 at 8:22 pm
not working propertly ;(
echo “o” | md5sum
e73af36376314c7c0022cb1d204f76b3
is different to this program
December 30th, 2007 at 12:54 am
depends on how do you validate it against
June 12th, 2008 at 11:37 pm
Hi.
I dont know why, but i cant open your example file with netbeans, can you give me any tip how to do it?
thanks