AES Java 多线程异常

Question

我注意到我正在运行的应用程序在同时解密时抛出异常。我写了以下内容来测试：

public void run() {
    for(int i=0; i<100000; i++){
        String encrypted = Crypt.encrypt(
                "Lorem ipsum dolor sit amet.",
                "password"
        );

        String decrypted = Crypt.decrypt(encrypted, "password")[0];
        System.out.println(decrypted);
    }
}


public static void main(String[] args) {

    Thread t1 = new Thread(new Main());
    Thread t2 = new Thread(new Main());

    t1.start();
    t2.start();

}

地穴方法如下：

public static String encrypt(String input, String key){

    try {

        byte[] ivBytes = new byte[16];
        SecureRandom.getInstance("SHA1PRNG").nextBytes(ivBytes);

        IvParameterSpec ips = new IvParameterSpec(ivBytes);
        byte[] keybytes = md5(key);//This isn't final. Don't worry ;)
        byte[] crypted = null;
        SecretKeySpec skey = new SecretKeySpec(keybytes, "AES");
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        cipher.init(Cipher.ENCRYPT_MODE, skey, ips);
        byte[] ptext = input.getBytes("UTF-8");
        crypted = cipher.doFinal(ptext);

        return Base64.encodeBase64String(ivBytes)+Base64.encodeBase64String(crypted);
    }catch(Exception e){
        e.printStackTrace();
    }
    return null;
}

public static String[] decrypt(String input, String key){

    String iv = input.substring(0, 24);
    String encrypted = input.substring(24);
    try {
        IvParameterSpec ips = new IvParameterSpec(Base64.decodeBase64(iv));
        byte[] keybytes = md5(key);//This isn't final. Don't worry ;)
        byte[] output = null;
        SecretKeySpec skey = new SecretKeySpec(keybytes, "AES");
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        cipher.init(Cipher.DECRYPT_MODE, skey, ips);
        output = cipher.doFinal(Base64.decodeBase64(encrypted));
        if(output==null){
            throw new Exception();
        }

        return new String[]{new String(output),iv};
    }catch(Exception e){
        e.printStackTrace();
    }
}

果然第一次尝试两个线程都失败了：

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.AESCipher.engineDoFinal(DashoA13*..)
at javax.crypto.Cipher.doFinal(DashoA13*..)
at common.Crypt.decrypt(Crypt.java:122)
at bootstrap.Main.run(Main.java:427)
at java.lang.Thread.run(Thread.java:680)

在每个线程上大约有 20 次尝试成功（大概是在不安全调用不相交的地方），然后抛出异常。这种模式似乎还在继续。

如果有帮助，我会在 OS X 10.7.2 上运行它。

如果我理解正确，这可能只是供应商问题，因为它使用的是 Sun JDK，我可以轻松换掉它，但我认为最好就此获得一些更有经验的意见并提出来，以防有人遇到偶然发现了同样的问题。

如果有人能指出线程安全加密+解密方案的方向，它可以达到相同的结果，我将不胜感激。

谢谢， 马库斯

Answer 1

问题是由用于从密码生成密钥的这一行引起的。

byte[] keybytes = md5(key);

使用 MessageDigest 类的 md5 函数很容易返回垃圾，这些垃圾随后被送入解密，最终失败。

Answer 2

public static String[] decrypt(String input, String key){

    String iv = input.substring(0, 24);
    String encrypted = input.substring(24);
    try {
        IvParameterSpec ips = new IvParameterSpec(Base64.decodeBase64(iv));
        byte[] keybytes = md5(key);//This isn't final. Don't worry ;)
        byte[] output = null;
        SecretKeySpec skey = new SecretKeySpec(keybytes, "AES");
        Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding"); //Change here
        cipher.init(Cipher.DECRYPT_MODE, skey, ips);
        output = cipher.doFinal(Base64.decodeBase64(encrypted));
        if(output==null){
            throw new Exception();
        }

        return new String[]{new String(output),iv};
    }catch(Exception e){
        e.printStackTrace();
    }
}