c# AES Decryption

核能气质少年 提交于 2019-11-30 07:36:34

There are actually multiple problems with your code. First in your decrypt method you're creating an encryptor, that should be a decryptor. Secondly you're reading the entire block including the padding of your algorithm into the buffer when you do the decryption. Below is a class with the items fixed and should be returning the proper result. I do however suggest you find a better way of storing the key, putting in your code and generating it the way you'r edoing it is a no no. You should generate your key with an RNG (RNGCryptoServiceProvider) then hash it with a secure hashing algorithm such as SHA512, use that output for your key. You then need to find a good place to store it, I would look into encrypting your web.config file.

public static class EncryptionHelper
{
    private static byte[] keyAndIvBytes;

    static EncryptionHelper()
    {
        // You'll need a more secure way of storing this, I hope this isn't
        // the real key
        keyAndIvBytes = UTF8Encoding.UTF8.GetBytes("tR7nR6wZHGjYMCuV");
    }

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

    public static byte[] StringToByteArray(string hex)
    {
        return Enumerable.Range(0, hex.Length)
                         .Where(x => x % 2 == 0)
                         .Select(x => Convert.ToByte(hex.Substring(x, 2), 16))
                         .ToArray();
    }

    public static string DecodeAndDecrypt(string cipherText)
    {
        string DecodeAndDecrypt = AesDecrypt(StringToByteArray(cipherText));
        return (DecodeAndDecrypt);
    }

    public static string EncryptAndEncode(string plaintext)
    {
        return ByteArrayToHexString(AesEncrypt(plaintext));
    }

    public static string AesDecrypt(Byte[] inputBytes)
    {
        Byte[] outputBytes = inputBytes;

        string plaintext = string.Empty;

        using (MemoryStream memoryStream = new MemoryStream(outputBytes))
        {
            using (CryptoStream cryptoStream = new CryptoStream(memoryStream, GetCryptoAlgorithm().CreateDecryptor(keyAndIvBytes, keyAndIvBytes), CryptoStreamMode.Read))
            {
                using (StreamReader srDecrypt = new StreamReader(cryptoStream))
                {
                    plaintext = srDecrypt.ReadToEnd();
                }
            }
        }

        return plaintext;
    }

    public static byte[] AesEncrypt(string inputText)
    {
        byte[] inputBytes = UTF8Encoding.UTF8.GetBytes(inputText);//AbHLlc5uLone0D1q

        byte[] result = null;
        using (MemoryStream memoryStream = new MemoryStream())
        {
            using (CryptoStream cryptoStream = new CryptoStream(memoryStream, GetCryptoAlgorithm().CreateEncryptor(keyAndIvBytes, keyAndIvBytes), CryptoStreamMode.Write))
            {
                cryptoStream.Write(inputBytes, 0, inputBytes.Length);
                cryptoStream.FlushFinalBlock();

                result = memoryStream.ToArray();
            }
        }

        return result;
    }


    private static RijndaelManaged GetCryptoAlgorithm()
    {
        RijndaelManaged algorithm = new RijndaelManaged();
        //set the mode, padding and block size
        algorithm.Padding = PaddingMode.PKCS7;
        algorithm.Mode = CipherMode.CBC;
        algorithm.KeySize = 128;
        algorithm.BlockSize = 128;
        return algorithm;
    }
}

Calling it is easy:

string crypt = "blahblahblah";
string EncryptAndEncode = EncryptionHelper.EncryptAndEncode(crypt);            
Console.WriteLine(EncryptAndEncode);

Console.WriteLine(EncryptionHelper.DecodeAndDecrypt(EncryptAndEncode));

Console.ReadLine();
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