public static void main(String[] args) {
		// TODO Auto-generated method stub


		try{

		   KeyPairGenerator clsKeyPairGenerator = KeyPairGenerator.getInstance("RSA");
		   clsKeyPairGenerator.initialize(2048);

		   KeyPair clsKeyPair = clsKeyPairGenerator.genKeyPair();
		   Key clsPublicKey = clsKeyPair.getPublic();
		   Key clsPrivateKey = clsKeyPair.getPrivate();
		   KeyFactory fact = KeyFactory.getInstance("RSA");
		   RSAPublicKeySpec clsPublicKeySpec = fact.getKeySpec( clsPublicKey, RSAPublicKeySpec.class);
		   RSAPrivateKeySpec clsPrivateKeySpec = fact.getKeySpec( clsPrivateKey, RSAPrivateKeySpec.class);
		   System.out.println( "public key modulus(" + clsPublicKeySpec.getModulus( ) + ") exponent(" + clsPublicKeySpec.getPublicExponent( ) + ")" );
		   System.out.println( "private key modulus(" + clsPrivateKeySpec.getModulus( ) + ") exponent(" + clsPrivateKeySpec.getPrivateExponent( ) + ")" );





		   BufferedReader in = new BufferedReader ( new InputStreamReader(System.in));

		   System.out.print("\n\n암호화할 문자열 입력 : ");


		   // 암호화 한다.
		   String strPinNumber = in.readLine();

		   Cipher clsCipher = Cipher.getInstance("RSA");
		   clsCipher.init( Cipher.ENCRYPT_MODE, clsPublicKey );
		    byte[] arrCipherData = clsCipher.doFinal( strPinNumber.getBytes( ) );
		    String strCipher = new String( arrCipherData );
		    System.out.println( "cipher : "  + strCipher );
		    // 복호화 한다.
		    clsCipher.init( Cipher.DECRYPT_MODE, clsPrivateKey );
		    byte[] arrData = clsCipher.doFinal( arrCipherData );

		    String strResult = new String( arrData );
		    System.out.println( "result : " + strResult);




		}catch( Exception e )
		  {
			   System.out.println("!! EXCEPTION !!");
			   e.printStackTrace();
		  }


	}