private void decrypt(File fileIn,String sKey){ 

try{ 

if(sKey.length() == 48){ 

String strPath = fileIn.getPath(); 

if(strPath.substring(strPath.length()-5).toLowerCase().equals(".tdes")) 

strPath = strPath.substring(0,strPath.length()-5); 

else{ 

JOptionPane.showMessageDialog(this,"不是合法的加密文件！",
"提示",JOptionPane.OK_OPTION); 

return; 

} 

JFileChooser chooser = new JFileChooser(); 

chooser.setCurrentDirectory(new File(".")); 

chooser.setSelectedFile(new File(strPath)); 

//用户指定要保存的文件 

int ret = chooser.showSaveDialog(this); 

if(ret==JFileChooser.APPROVE_OPTION){ 

byte[] bytK1 = getKeyByStr(sKey.substring(0,16)); 

byte[] bytK2 = getKeyByStr(sKey.substring(16,32)); 

byte[] bytK3 = getKeyByStr(sKey.substring(32,48)); 

FileInputStream fis = new FileInputStream(fileIn); 

byte[] bytIn = new byte[(int)fileIn.length()]; 

for(int i = 0;i< fileIn.length();i++){ 

bytIn[i] = (byte)fis.read(); 

} 

//解密 

byte[] bytOut = decryptByDES(decryptByDES(decryptByDES(bytIn,bytK3),bytK2),bytK1); 

File fileOut = chooser.getSelectedFile(); 

fileOut.createNewFile(); 

FileOutputStream fos = new FileOutputStream(fileOut); 

for(int i = 0;i< bytOut.length;i++){ 

fos.write((int)bytOut[i]); 

} 

fos.close(); 

JOptionPane.showMessageDialog(this,"解密成功！","提示",JOptionPane.OK_OPTION); 

} 

}else 

JOptionPane.showMessageDialog(this,"密码长度必须等于48！",
"错误信息",JOptionPane.ERROR_MESSAGE); 

}catch(Exception e){ 

JOptionPane.showMessageDialog(this,"解密失败，请核对密码！",
"提示",JOptionPane.OK_OPTION); 

} 

} 

private byte[] encryptByDES(byte[] bytP,byte[] bytKey) throws Exception{ 

DESKeySpec desKS = new DESKeySpec(bytKey); 

SecretKeyFactory skf = SecretKeyFactory.getInstance("DES"); 

SecretKey sk = skf.generateSecret(desKS); 

Cipher cip = Cipher.getInstance("DES"); 

cip.init(Cipher.ENCRYPT_MODE,sk); 

return cip.doFinal(bytP); 

} 

private byte[] decryptByDES(byte[] bytE,byte[] bytKey) throws Exception{ 

DESKeySpec desKS = new DESKeySpec(bytKey); 

SecretKeyFactory skf = SecretKeyFactory.getInstance("DES"); 

SecretKey sk = skf.generateSecret(desKS); 

Cipher cip = Cipher.getInstance("DES"); 

cip.init(Cipher.DECRYPT_MODE,sk); 

return cip.doFinal(bytE); 

}