javax.crypto.BadPaddingException: Given final block not properly padded 解决方法

下面的 Des 加密解密代码，在加密时正常，但是在解密是抛出错误：

javax.crypto.BadPaddingException: Given final block not properly padded
at com.sun.crypto.provider.SunJCE_f.b(DashoA13*..)
at com.sun.crypto.provider.SunJCE_f.b(DashoA13*..)
at com.sun.crypto.provider.DESCipher.engineDoFinal(DashoA13*..)
at javax.crypto.Cipher.doFinal(DashoA13*..)

　

public class Des {
static Des instance;
static Key key;
static Cipher encryptCipher;
static Cipher decryptCipher;

protected Des() {
}

protected Des(String strKey) {
key = setKey(strKey);
try {
encryptCipher = Cipher.getInstance("DES");
encryptCipher.init(Cipher.ENCRYPT_MODE, key);
decryptCipher = Cipher.getInstance("DES");
decryptCipher.init(Cipher.DECRYPT_MODE, key);
} catch (NoSuchAlgorithmException e) {
e.printStackTrace();
} catch (NoSuchPaddingException e) {
e.printStackTrace();
} catch (InvalidKeyException e) {
e.printStackTrace();
}

}

public static Des getInstance() {
if (instance == null) {
instance = new Des("diaxxxxoft@201Y10");
}

return instance;
}

//  根据参数生成KEY
private Key setKey(String strKey) {
try {
KeyGenerator _generator = KeyGenerator.getInstance("DES");
_generator.init(new SecureRandom(strKey.getBytes()));
return _generator.generateKey();

} catch (Exception e) {
e.printStackTrace();
}

return null;
}

//  加密String明文输入,String密文输出
public String setEncString(String strMing) {
BASE64Encoder base64en = new BASE64Encoder();
try {
byte[] byteMing = strMing.getBytes("UTF-8");
byte[] byteMi = this.getEncCode(byteMing);
return base64en.encode(byteMi);
} catch (Exception e) {
e.printStackTrace();
}
return null;
}

//加密以byte[]明文输入,byte[]密文输出
private byte[] getEncCode(byte[] byteS) {
byte[] byteFina = null;
try {
byteFina = encryptCipher.doFinal(byteS);
} catch (Exception e) {
e.printStackTrace();
}
return byteFina;
}

//	 解密:以String密文输入,String明文输出
public String setDesString(String strMi) {
BASE64Decoder base64De = new BASE64Decoder();
try {
byte[] byteMi = base64De.decodeBuffer(strMi);
byte[] byteMing = this.getDesCode(byteMi);
return new String(byteMing, "UTF-8");
} catch (Exception e) {
e.printStackTrace();
}
return null;
}

// 解密以byte[]密文输入,以byte[]明文输出
private byte[] getDesCode(byte[] byteD) {
byte[] byteFina = null;
try {
byteFina = decryptCipher.doFinal(byteD);
} catch (Exception e) {
e.printStackTrace();
}
return byteFina;
}

//多线程测试一下
public static void main(String[] args) throws InterruptedException {

//没有依赖注入的配置，所以在这里手动生成一次
Des dtDes = Des.getInstance();

final String[] mi = new String[10];
for (int i = 0; i < 10; i++) {
final Integer integer = i;
Thread thread = new Thread() {
public void run() {
//明文加密：
Des dtDes = Des.getInstance();
mi[integer] = dtDes.setEncString("ShowHistory.jsp?MenuId=345&MenuBelong=1&tableLimits=where a1450=RecordId"); //调用get函数获取加密后密文。
}
};
thread.start();
}

Thread.sleep(5000);

for (int i = 0; i < 10; i++) {
final Integer integer = i;

Thread thread2 = new Thread() {
public void run() {
System.out.println(String.format("mi[%s] = %s", integer, mi[integer]));
//这样来模拟另外一个页面的获取
Des dtDes2 = Des.getInstance();
String M = dtDes2.setDesString(mi[integer]);//调用get函数获取解密后明文。
System.out.println(String.format("des[%s] = %s", integer, M));
}
};
thread2.start();
}

//等待打印完毕
Thread.sleep(5000);
}
}

解决方法：

将 setKey方法修改为如下：

//  根据参数生成KEY
private Key setKey(String strKey) {
try {
SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
DESKeySpec keySpec = new DESKeySpec(strKey.getBytes("utf-8"));
keyFactory.generateSecret(keySpec);
return keyFactory.generateSecret(keySpec);
} catch (Exception e) {
e.printStackTrace();
}

return null;
}

不使用SecureRandom生成SecretKey，而是使用SecretKeyFactory；重新实现方法generateKey，代码如下

问题解决。

另外如果 加密时 和解密 时使用的秘钥 不一样，也会报 相同的错误。

比如加密时使用的秘钥：

diaxxxxoft@201xxxx10

而解密时使用的秘钥：

addddxxxx

那么在解密时也可能会报这个错误。