Unable to decrypt back plainText using TripleDESCryptoServiceProvider

Question

I'm trying to encrypt and decrypt text using TripleDESCryptoServiceProvider.

My requirement is for same plaintext, ciphertext should not be same, for this I have generated different vector each time.

This is code to Encrypt and Decrypt text.

public string EncryptString(string PlainText)
        {
            GenerateIV();
            GenerateKey();
            if (PlainText == null || PlainText.Length <= 0)
            {
                throw new ArgumentNullException("Invalid Plaintext.");
            }

            if (Key == null || Key.Length <= 0)
            {
                throw new ArgumentNullException("Key Can Not Be Null Or Empty.");
            }

            if (IV == null || IV.Length <= 0)
            {
                throw new ArgumentNullException("Vector Can Not Be Null Or Empty.");
            }

            byte[] encryptedText;

            using (TripleDESCryptoServiceProvider tdsObj = new TripleDESCryptoServiceProvider())
            {
                if (!isKeyStrengthChecked)
                {
                    bool isWeekKey = TripleDESCryptoServiceProvider.IsWeakKey(Key);
                    if (isWeekKey)
                    {
                        throw new Exception("Weak Key.");
                    }
                    else
                    {
                        isKeyStrengthChecked = true;
                    }
                }
                tdsObj.Key = Key;
                tdsObj.IV = IV;
                tdsObj.Mode = CipherMode.CBC;
                tdsObj.Padding = PaddingMode.PKCS7;
                ICryptoTransform encryptor = tdsObj.CreateEncryptor(tdsObj.Key, tdsObj.IV);
                using (MemoryStream msEncrypt = new MemoryStream())
                {
                    using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
                    {
                        using (StreamWriter srEncrypt = new StreamWriter(csEncrypt))
                        {
                            srEncrypt.Write(PlainText);
                        }
                        encryptedText = msEncrypt.ToArray();
                    }
                }
            }
            return Convert.ToBase64String(encryptedText);
        }

        public string DecryptString(string cipherText)
        {
            GenerateIV();
            GenerateKey();
            if (cipherText == null || cipherText.Length <= 0)
            {
                throw new ArgumentNullException("Invalid CipherText.");
            }

            if (Key == null || Key.Length <= 0)
            {
                throw new ArgumentNullException("Key Can Not Be Null Or Empty.");
            }

            if (IV == null || IV.Length <= 0)
            {
                throw new ArgumentNullException("Vector Can Not Be Null Or Empty.");
            }

            byte[] cipherBytes = Convert.FromBase64String(cipherText);
            string PlainText = null;
            using (TripleDESCryptoServiceProvider tdsDecrypt = new TripleDESCryptoServiceProvider())
            {
                tdsDecrypt.Key = Key;
                tdsDecrypt.IV = IV;
                tdsDecrypt.Mode = CipherMode.CBC;
                tdsDecrypt.Padding = PaddingMode.PKCS7;
                ICryptoTransform decrytor = tdsDecrypt.CreateDecryptor(Key, IV);
                using (MemoryStream msDecrypt = new MemoryStream(cipherBytes))
                {
                    using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decrytor, CryptoStreamMode.Read))
                    {
                        using (StreamReader srDecrypt = new StreamReader(csDecrypt))
                        {
                            PlainText = srDecrypt.ReadToEnd();
                        }
                    }
                }
            }
            return PlainText;
        }

My complete Code Is Here .Net Fiddle

But when I decrypt Text, I'm not getting the same plain text. What's wrong I have Done.

Answer 1

Try this

Dotnet Fiddle Demo

Comment // GenerateIV(); GenerateKey(); on both EncryptString and DecryptString function

        string plainText1 = "Hello Amit";
        string plainText2 = "Hello Amit";
        Helper helper = new Helper();

        helper.GenerateIV();
        helper.GenerateKey();
        string encryptedData1 = helper.EncryptString(plainText1);
        string encryptedData2 = helper.EncryptString(plainText2);
        string getBackText = helper.DecryptString(encryptedData1);
        Console.WriteLine(getBackText);
        Console.ReadLine();

Answer 2

You generate new IV and key with the decrypt call

public string DecryptString(string cipherText)
    {
        GenerateIV();
        GenerateKey();
        if (cipherText == null || cipherText.Length <= 0)

You should use the same IV and key on both encrypt and decrypt