由 C# AES 解密

Question

我正在尝试通过 AES 在 C# 中制作一个 encrypt/decrypt 程序。这是我的代码：

using System;
using System.IO;
using System.Text;
using System.Linq;
using System.Security.Cryptography;

namespace encryptingApp
{
    public class AES_Crypt
    {
        public static void Main ()
        {
            string text = "this-needs-to-be-encrypted";

            string IV = "0000000000000000";

            int ivBlockSize = 16;

            string key = "00000000000000000000000000000000";

            int keySize = 32;

            string encriptedText = Encrypt(text,key,IV);

            string decrypted = Decrypt(encriptedText, key, ivBlockSize);

        }


        public static string Encrypt(string clearText, string key, string iv )
        {

            byte[] textBytes=GetBytes(clearText);


            using (Aes encryptor = Aes.Create())
            {
                encryptor.IV =  GetBytes(iv);
                encryptor.Key = GetBytes(key);

                using (MemoryStream ms = new MemoryStream())
                {

                    using (CryptoStream cs = new CryptoStream(ms, encryptor.CreateEncryptor(encryptor.Key,encryptor.IV), CryptoStreamMode.Write))
                    {
                        cs.Write(textBytes, 0, textBytes.Length);
                        cs.Close();
                    }
                    string rv= iv + ByteToHex(ms.ToArray()).ToLower();

                    clearText = Base64Encode(rv);
                }
            }
            return clearText;
        }



       public static string Decrypt(string encriptedText, string key, int ivBlockSize)
       {
           string decryptedText = null;

           string fullText=Base64Decode(encriptedText);

           string realIV = fullText.Substring( 0 , ivBlockSize );

           string cypherText = fullText.Substring(ivBlockSize, fullText.Length - ivBlockSize - 1);


            byte[] cypherTextInBytes = HexToByte(cypherText);

            using (Aes decryptor = Aes.Create())
            {     
                decryptor.Key = GetBytes(key);

                decryptor.IV = GetBytes(realIV);

                decryptor.Mode = CipherMode.CBC;  

                using (MemoryStream ms = new MemoryStream())
                {
                    using (CryptoStream cs = new CryptoStream(ms, decryptor.CreateDecryptor(decryptor.Key,decryptor.IV), CryptoStreamMode.Read))
                    {
                        using (var sr = new StreamReader(cs))
                        {
                            decryptedText = sr.ReadToEnd();
                        }

                    }

                }
            }
            return decryptedText;
        }

        static byte[] GetBytes(string str)
        {
            return System.Text.Encoding.UTF8.GetBytes(str);
        }

        static string GetString(byte[] bytes)
        {
            return System.Text.Encoding.UTF8.GetString(bytes);
        }

        public static string Base64Encode(string plainText)
        {
                var plainTextBytes = System.Text.Encoding.UTF8.GetBytes(plainText);
                return System.Convert.ToBase64String(plainTextBytes);
        }

        public static string Base64Decode(string base64EncodedData)
        {
            var base64EncodedBytes = System.Convert.FromBase64String(base64EncodedData);
            return System.Text.Encoding.UTF8.GetString(base64EncodedBytes);
        }

        public static string ByteToHex(byte[] ba)
        {
            return BitConverter.ToString(ba).Replace("-", "").ToLower();
        }


        public static byte[] HexToByte(string hex)
        {

            byte[] arr = new byte[hex.Length >> 1];

            for (int i = 0; i < hex.Length >> 1; ++i)
            {
                arr[i] = (byte)((GetHexVal(hex[i << 1]) << 4) + (GetHexVal(hex[(i << 1) + 1])));
            }

            return arr;
        }

        public static int GetHexVal(char hex) 
        {
            int val = (int) hex;
            return val - (val < 58 ? 48 : 87);
        }


    }
}

Encrypt 函数非常出色，returns 我得到了正确的加密文本。问题存在于 Decrypt 函数中，一切顺利（我一直在屏幕上打印我的变量），直到 StreamReader 使用 .ReadToEnd()。我得到一个 CryptographyException（我在一次执行中两次得到相同的异常）：

Unhandled Exception:
System.Security.Cryptography.CryptographicException: Bad PKCS7 padding. Invalid length 0.        
at Mono.Security.Cryptography.SymmetricTransform.ThrowBadPaddingException (System.Security.Cryptography.PaddingMode padding, System.Int32 length, System.Int32 position) [0x0005c] in <8f2c484307284b51944a1a13a14c0266>:0 
at Mono.Security.Cryptography.SymmetricTransform.FinalDecrypt (System.Byte[] inputBuffer, System.Int32 inputOffset, System.Int32 inputCount) [0x00179] in <8f2c484307284b51944a1a13a14c0266>:0 
at Mono.Security.Cryptography.SymmetricTransform.TransformFinalBlock (System.Byte[] inputBuffer, System.Int32 inputOffset, System.Int32 inputCount) [0x00034] in <8f2c484307284b51944a1a13a14c0266>:0 
at System.Security.Cryptography.CryptoStream.Read (System.Byte[] buffer, System.Int32 offset, System.Int32 count) [0x00318] in <8f2c484307284b51944a1a13a14c0266>:0 
at System.IO.StreamReader.ReadBuffer () [0x0002b] in <8f2c484307284b51944a1a13a14c0266>:0 
at System.IO.StreamReader.ReadToEnd () [0x00055] in <8f2c484307284b51944a1a13a14c0266>:0 
at encryptingApp.AES_Crypt.Decrypt (System.String encriptedText, System.String key, System.Int32 ivBlockSize) [0x000e4] in <f27b48dde1ea4b788e8038439b4bdb55>:0 
at encryptingApp.AES_Crypt.Main () [0x000e0] in <f27b48dde1ea4b788e8038439b4bdb55>:0


[ERROR] FATAL UNHANDLED EXCEPTION: System.Security.Cryptography.CryptographicException: Bad PKCS7 padding. Invalid length 0.    
at Mono.Security.Cryptography.SymmetricTransform.ThrowBadPaddingException (System.Security.Cryptography.PaddingMode padding, System.Int32 length, System.Int32 position) [0x0005c] in <8f2c484307284b51944a1a13a14c0266>:0 
at Mono.Security.Cryptography.SymmetricTransform.FinalDecrypt (System.Byte[] inputBuffer, System.Int32 inputOffset, System.Int32 inputCount) [0x00179] in <8f2c484307284b51944a1a13a14c0266>:0 
at Mono.Security.Cryptography.SymmetricTransform.TransformFinalBlock (System.Byte[] inputBuffer, System.Int32 inputOffset, System.Int32 inputCount) [0x00034] in <8f2c484307284b51944a1a13a14c0266>:0 
at System.Security.Cryptography.CryptoStream.FlushFinalBlock () [0x0001b] in <8f2c484307284b51944a1a13a14c0266>:0 
at System.Security.Cryptography.CryptoStream.Dispose (System.Boolean disposing) [0x00011] in <8f2c484307284b51944a1a13a14c0266>:0 
at System.IO.Stream.Close () [0x00000] in <8f2c484307284b51944a1a13a14c0266>:0 
at System.IO.StreamReader.Dispose (System.Boolean disposing) [0x0001c] in <8f2c484307284b51944a1a13a14c0266>:0 
at System.IO.TextReader.Dispose () [0x00000] in <8f2c484307284b51944a1a13a14c0266>:0 
at encryptingApp.AES_Crypt.Decrypt (System.String encriptedText, System.String key, System.Int32 ivBlockSize) [0x000f8] in <f27b48dde1ea4b788e8038439b4bdb55>:0 
at encryptingApp.AES_Crypt.Main () [0x000e0] in <f27b48dde1ea4b788e8038439b4bdb55>:0

我想我应该修复 Streamreader，但我不知道该怎么做，我已经在这里待了几个小时了！该程序似乎正在尝试读取长度为 0 或其他内容的内容。

我什至尝试在互联网上寻找更多解密功能，但 none 对我有用（我在没有 RijndaelManaged 或盐的情况下这样做）。我在 MacOS 中编译。

Answer 1

为什么你的代码中有这么多字符串？密码学以字节为单位，去掉所有的字符串。

您的 IV（理想情况下应该是 Encrypt generated/emitted，而不是传递给它）被读取为 UTF-8 字符串。如果它有任何不在 ASCII 0-127 中的字符，它就不会有 1:1 字符串长度到 byte[] 长度。
- 你也很难提供一个带有 iv 0x00000000000000000000000000000003 的字符串
与您的密钥类似。
您作为 IV+Ciphertext blob Base64Encode(UTF8Bytes(Concat(ivString, Hex(ciphertextBytes)))) 发出。
- Base64Encode(Concat(ivBytes, ciphertextBytes)) 涉及少两个转换。所以它更不容易出错，而且速度更快。
当您进入 Decrypt 时，您会正确应用所有转换以撤消您所做的操作，但您需要从外部知道有多少字符构成了 IV。由于您已经将 UTF8 处理添加到混合中，您实际上并不知道它。
- 因此您的 Decrypt IV 得到以下处理
  - Base64解码
  - UTF8BytesToString
  - 子串
  - UTF8StringToBytes
- 如果不涉及字符串，您只需使用 Base64Decode 和 Copy。

我的直觉是，如果您将所有事情都视为 byte[]，您的问题就会消失。（是的，您要保护的数据可以是文本，因此立即使用 UTF8StringToBytes 就可以了）

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