How to generate key pair using java ?(its urgent)

Question

We r working on java card. For security purpose I want a Key pair.
If anyone is able to uide me by giving me a small code or algorithm i am very thankful.
Its an urgent !!!!
Plz inform me if any relative information u r having.

Answer 1

import java.security.KeyPairGenerator;
import java.security.KeyPair;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SecureRandom;
import java.security.KeyFactory;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.io.FileOutputStream;
import java.io.FileInputStream;
public class ParClaves {
     public KeyPairGenerator keyPairGenerator;
     public KeyPair keyPair;
     public PrivateKey privateKey;
     public PublicKey publicKey;
     public String algoritmo = "DSA"; // DSA o RSA
     public String proveedor = null;
     public int keysize = 1024;
     public SecureRandom random = null;
     public void guardarClaves(String fichClavePublica, String fichClavePrivada) throws Exception {
          byte[] key = this.publicKey.getEncoded();
          FileOutputStream keyfos = new FileOutputStream(fichClavePublica);
          keyfos.write(key);
          keyfos.close();               
          key = this.privateKey.getEncoded();
          keyfos = new FileOutputStream(fichClavePrivada);
          keyfos.write(key);
          keyfos.close();               
     } // fin de guardarClaves
     public void guardarClaves(String fichClavePublica, String fichClavePrivada, KeyPair keyPair) throws Exception {
          byte[] key = keyPair.getPublic().getEncoded();
          FileOutputStream keyfos = new FileOutputStream(fichClavePublica);
          keyfos.write(key);
          keyfos.close();               
          key = keyPair.getPrivate().getEncoded();
          keyfos = new FileOutputStream(fichClavePrivada);
          keyfos.write(key);
          keyfos.close();               
     } // fin de guardarClaves     
     public KeyPair recuperarClaves(String fichClavePublica, String fichClavePrivada) throws Exception {
          return new KeyPair(recuperarClavePublica(fichClavePublica), recuperarClavePrivada(fichClavePrivada));
     } // fin de recuperarClaves
     public PublicKey recuperarClavePublica(String fichClavePublica) throws Exception {
// PENDIENTE: seguramente, para que esto fuera v�lido, habr�a que proporcionar el Proveedor ?�
// probar generando clavePublica con otro proveedor distinto de SUN
          FileInputStream fis = new FileInputStream(fichClavePublica);
          byte[] encKey = new byte[fis.available()];
          fis.read(encKey);
          fis.close();
          KeyFactory keyFactory = null;
          try {
               keyFactory = KeyFactory.getInstance("DSA");
          } catch (Exception e) {
               keyFactory = KeyFactory.getInstance("RSA");
          } // fin del try
          X509EncodedKeySpec pubKeySpecX509 = new X509EncodedKeySpec(encKey);
          PublicKey publicKey = keyFactory.generatePublic(pubKeySpecX509);
          return publicKey;
     } // fin de recuperarClavePublica
     public PrivateKey recuperarClavePrivada(String fichClavePrivada) throws Exception {
// PENDIENTE: seguramente, para que esto fuera v�lido, habr�a que proporcionar el Proveedor ?�
// probar generando clavePrivada con otro proveedor distinto de SUN
          FileInputStream fis = new FileInputStream(fichClavePrivada);
          byte[] encKey = new byte[fis.available()];
          fis.read(encKey);
          fis.close();
          KeyFactory keyFactory = null;
          try {
               keyFactory = KeyFactory.getInstance("DSA");
          } catch (Exception e) {
               keyFactory = KeyFactory.getInstance("RSA");
          } // fin del try
          PKCS8EncodedKeySpec privKeySpecPKCS8 = new PKCS8EncodedKeySpec(encKey);
          PrivateKey privateKey = keyFactory.generatePrivate(privKeySpecPKCS8);
          return privateKey;
     } // fin de recuperarClavePrivada
     public KeyPair generarClaves() throws Exception {
          if (this.proveedor == null) {
               this.keyPairGenerator = KeyPairGenerator.getInstance(this.algoritmo);
               this.proveedor = this.keyPairGenerator.getProvider().getName();
          } else {
               this.keyPairGenerator = KeyPairGenerator.getInstance(this.algoritmo, this.proveedor);
          } // fin del if
          if (this.random == null) {
               this.keyPairGenerator.initialize(this.keysize);
          } else {
               this.keyPairGenerator.initialize(this.keysize, this.random);
          } // fin del if
          this.keyPair = this.keyPairGenerator.generateKeyPair();
          this.privateKey = this.keyPair.getPrivate();
          this.publicKey = this.keyPair.getPublic();
          return this.keyPair;
     } // fin de generarClaves
     public KeyPair generarClaves(SecureRandom random) throws Exception {
          this.random = random;
          return generarClaves();
     } // fin de generarClaves
     public KeyPair generarClaves(int keysize) throws Exception {
          this.keysize = keysize;
          return generarClaves();
     } // fin de generarClaves
     public KeyPair generarClaves(int keysize, SecureRandom random) throws Exception {
          this.keysize = keysize;
          this.random = random;          
          return generarClaves();
     } // fin de generarClaves
     public KeyPair generarClaves(String algoritmoOproveedor) throws Exception {
          decidir(algoritmoOproveedor);
          return generarClaves();
     } // fin de generarClaves
     public KeyPair generarClaves(String algoritmoOproveedor, SecureRandom random) throws Exception {
          decidir(algoritmoOproveedor);
          this.random = random;          
          return generarClaves();
     } // fin de generarClaves
     public KeyPair generarClaves(String algoritmoOproveedor, int keysize) throws Exception {
          decidir(algoritmoOproveedor);
          this.keysize = keysize;          
          return generarClaves();
     } // fin de generarClaves
     public KeyPair generarClaves(String algoritmoOproveedor, int keysize, SecureRandom random) throws Exception {
          decidir(algoritmoOproveedor);
          this.keysize = keysize;          
          this.random = random;                    
          return generarClaves();
     } // fin de generarClaves
     public KeyPair generarClaves(String algoritmo, String proveedor) throws Exception {
          this.algoritmo = algoritmo;          
          this.proveedor = proveedor;                    
          return generarClaves();
     } // fin de generarClaves
     public KeyPair generarClaves(String algoritmo, String proveedor, SecureRandom random) throws Exception {
          this.algoritmo = algoritmo;          
          this.proveedor = proveedor;
          this.random = random;                              
          return generarClaves();
     } // fin de generarClaves
     public KeyPair generarClaves(String algoritmo, String proveedor, int keysize) throws Exception {
          this.algoritmo = algoritmo;          
          this.proveedor = proveedor;
          this.keysize = keysize;                              
          return generarClaves();
     } // fin de generarClaves
     public KeyPair generarClaves(String algoritmo, String proveedor, int keysize, SecureRandom random) throws Exception {
          this.algoritmo = algoritmo;          
          this.proveedor = proveedor;
          this.keysize = keysize;
          this.random = random;          
          return generarClaves();
     } // fin de generarClaves
     public String getInformacion() {
          StringBuffer sb = new StringBuffer();
          sb.append("Algoritmo: " + this.algoritmo + "\n");
          sb.append("Proveedor: " + this.proveedor + "\n");
          sb.append("Keysize: " + this.keysize + "\n");
          return sb.toString();
     } // fin de getInformacion
     public boolean esAlgoritmoValido(String algoritmo) {
          try {
               KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(algoritmo);
               return true;
          } catch (Exception e) {
               return false;
          } // fin del try
     } // fin de esAlgoritmoValido
     private void decidir(String algoritmoOproveedor) {
          if (esAlgoritmoValido(algoritmoOproveedor)) {
               this.algoritmo = algoritmoOproveedor;
          } else {
               this.proveedor = algoritmoOproveedor;
          } // fin del if
     } // fin de decidir
} // fin de ParClaves