Android中AES的java解密算法

Question

public static String Encrypt(String text){
    try {           
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        byte[] keyBytes= new byte[16];
        byte[] b= KEY.getBytes("UTF-8");
        int len= b.length;
        if (len > keyBytes.length) len = keyBytes.length;
        System.arraycopy(b, 0, keyBytes, 0, len);
        SecretKeySpec keySpec = new SecretKeySpec(keyBytes, "AES");
        IvParameterSpec ivSpec = new IvParameterSpec(keyBytes);
        cipher.init(Cipher.ENCRYPT_MODE,keySpec,ivSpec);

        byte[] results = cipher.doFinal(text.getBytes("UTF-8"));
        String result = Base64.encodeToString(results, 0);
        //result = URLEncoder.encode(result.trim(),"UTF-8");
        return result;

    } catch (Exception e) {
        // TODO: handle exception
        return null;
    }
}   

public static String Decrypt(String text){
    try {           
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        byte[] keyBytes= new byte[16];
        byte[] b= KEY.getBytes("UTF-8");
        int len= b.length;
        if (len > keyBytes.length) len = keyBytes.length;
        System.arraycopy(b, 0, keyBytes, 0, len);
        SecretKeySpec keySpec = new SecretKeySpec(keyBytes, "AES");
        IvParameterSpec ivSpec = new IvParameterSpec(keyBytes);
        cipher.init(Cipher.DECRYPT_MODE,keySpec,ivSpec);
        byte[] results = cipher.doFinal(text.getBytes("UTF-8"));
        String result = Base64.encodeToString(results, 0);
        //result = URLEncoder.encode(result.trim(),"UTF-8");
        return result;

    } catch (Exception e) {
        // TODO: handle exception
        Log.d("decryption", e.getMessage());
        return null;
    }
}   

这是加密和解密的代码，我从另一个问题得到了加密算法，它对我来说很好，但我也需要解密，我试着像加密一样模拟它，但它不起作用。异常显示最后一个块未完成

Answer 1

问题是你没有按相反的顺序执行相反的顺序。你最终得到了base64编码的数据——所以你需要做的第一件事是base64解码，以获得二进制加密数据。然后解密，然后使用UTF-8将其转换回字符串

public static String decrypt(String text){
    try {           
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        byte[] keyBytes= new byte[16];
        byte[] b= KEY.getBytes("UTF-8");
        int len= b.length;
        if (len > keyBytes.length) len = keyBytes.length;
        System.arraycopy(b, 0, keyBytes, 0, len);
        SecretKeySpec keySpec = new SecretKeySpec(keyBytes, "AES");
        IvParameterSpec ivSpec = new IvParameterSpec(keyBytes);
        cipher.init(Cipher.DECRYPT_MODE,keySpec,ivSpec);
        byte[] results = cipher.doFinal(Base64.decode(text, 0));
        return new String(results, "UTF-8");
    } catch (Exception e) {
        // TODO: handle exception
        Log.d("decryption", e.getMessage());
        return null;
    }
}   

当你从某个地方获取代码时，真正理解它在做什么是很重要的，尤其是要理解每个阶段的数据是什么样的：

• 从纯文本开始
• UTF-8将其编码为字节数组
• 加密到另一个字节数组（它不是UTF-8编码的文本）
• Base64将加密的二进制数据编码为字符串

任何时候你在做这样的转换，当你想要反转它时，你也需要反转步骤的顺序，以便回到原始数据