Расшифровать строку с помощью Rijndael, возвращающего System.SecureString (как строку), но не строку

Я реализовал rijndael в прошлом, и вот моя версия, если это поможет:

private static string Encrypt(string plainText, string passPhrase, string saltValue, string hashAlgorithm, int passwordIterations, string initVector, int keySize)
        {
            // Convert strings into byte arrays.
            // Let us assume that strings only contain ASCII codes.
            // If strings include Unicode characters, use Unicode, UTF7, or UTF8 
            // encoding.
            var initVectorBytes = Encoding.ASCII.GetBytes(initVector);
            var saltValueBytes = Encoding.ASCII.GetBytes(saltValue);

            // Convert our plaintext into a byte array.
            // Let us assume that plaintext contains UTF8-encoded characters.
            var plainTextBytes = Encoding.UTF8.GetBytes(plainText);

            // First, we must create a password, from which the key will be derived.
            // This password will be generated from the specified passphrase and 
            // salt value. The password will be created using the specified hash 
            // algorithm. Password creation can be done in several iterations.
            var password = new PasswordDeriveBytes(passPhrase, saltValueBytes, hashAlgorithm, passwordIterations);

            // Use the password to generate pseudo-random bytes for the encryption
            // key. Specify the size of the key in bytes (instead of bits).
            var keyBytes = password.GetBytes(keySize / 8);

            // Create uninitialized Rijndael encryption object.

            // It is reasonable to set encryption mode to Cipher Block Chaining
            // (CBC). Use default options for other symmetric key parameters.
            var symmetricKey = new RijndaelManaged { Mode = CipherMode.CBC };

            // Generate encryptor from the existing key bytes and initialization 
            // vector. Key size will be defined based on the number of the key 
            // bytes.
            var encryptor = symmetricKey.CreateEncryptor(keyBytes, initVectorBytes);

            // Define memory stream which will be used to hold encrypted data.
            var memoryStream = new MemoryStream();

            // Define cryptographic stream (always use Write mode for encryption).
            var cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write);

            // Start encrypting.
            cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length);

            // Finish encrypting.
            cryptoStream.FlushFinalBlock();

            // Convert our encrypted data from a memory stream into a byte array.
            var cipherTextBytes = memoryStream.ToArray();

            // Close both streams.
            memoryStream.Close();
            cryptoStream.Close();

            // Convert encrypted data into a base64-encoded string.
            var cipherText = Convert.ToBase64String(cipherTextBytes);

            // Return encrypted string.
            return cipherText;
        }


private static string Decrypt(string cipherText, string passPhrase, string saltValue, string hashAlgorithm, int passwordIterations, string initVector, int keySize)
        {
            // Convert strings defining encryption key characteristics into byte
            // arrays. Let us assume that strings only contain ASCII codes.
            // If strings include Unicode characters, use Unicode, UTF7, or UTF8
            // encoding.
            var initVectorBytes = Encoding.ASCII.GetBytes(initVector);
            var saltValueBytes = Encoding.ASCII.GetBytes(saltValue);

            // Convert our ciphertext into a byte array.
            var cipherTextBytes = Convert.FromBase64String(cipherText);

            // First, we must create a password, from which the key will be 
            // derived. This password will be generated from the specified 
            // passphrase and salt value. The password will be created using
            // the specified hash algorithm. Password creation can be done in
            // several iterations.
            var password = new PasswordDeriveBytes(passPhrase, saltValueBytes, hashAlgorithm, passwordIterations);

            // Use the password to generate pseudo-random bytes for the encryption
            // key. Specify the size of the key in bytes (instead of bits).
            var keyBytes = password.GetBytes(keySize / 8);

            // Create uninitialized Rijndael encryption object.
            // It is reasonable to set encryption mode to Cipher Block Chaining
            // (CBC). Use default options for other symmetric key parameters.
            var symmetricKey = new RijndaelManaged { Mode = CipherMode.CBC };

            // Generate decryptor from the existing key bytes and initialization 
            // vector. Key size will be defined based on the number of the key 
            // bytes.
            var decryptor = symmetricKey.CreateDecryptor(keyBytes, initVectorBytes);

            // Define memory stream which will be used to hold encrypted data.
            var memoryStream = new MemoryStream(cipherTextBytes);

            // Define cryptographic stream (always use Read mode for encryption).
            var cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read);

            // Since at this point we don't know what the size of decrypted data
            // will be, allocate the buffer long enough to hold ciphertext;
            // plaintext is never longer than ciphertext.
            var plainTextBytes = new byte[cipherTextBytes.Length];

            // Start decrypting.
            var decryptedByteCount = cryptoStream.Read(plainTextBytes, 0, plainTextBytes.Length);

            // Close both streams.
            memoryStream.Close();
            cryptoStream.Close();

            // Convert decrypted data into a string. 
            // Let us assume that the original plaintext string was UTF8-encoded.
            var plainText = Encoding.UTF8.GetString(plainTextBytes, 0, decryptedByteCount);

            // Return decrypted string.   
            return plainText;
        }

public static string EncryptData(string encryptText, string passPhrase, string saltValue, string hashAlgorithm, int passwordIterations, string initVector, int keySize)
{
    return Encrypt(encryptText, passPhrase, saltValue, hashAlgorithm, passwordIterations, initVector, keySize);
}

public static string DecryptData(string decryptText, string passPhrase, string saltValue, string hashAlgorithm, int passwordIterations, string initVector, int keySize)
{
    return Decrypt(decryptText, passPhrase, saltValue, hashAlgorithm, passwordIterations, initVector, keySize);
}

Затем у меня были некоторые общедоступные методы, которые вызывают вышеуказанные методы...

public static string EncryptData(string encryptText)
{
    return EncryptionHelper.EncryptData(encryptText, ConfigHelper.PassPhrase, ConfigHelper.SaltValue, ConfigHelper.HashAlgorithm, ConfigHelper.PasswordIterations, ConfigHelper.InitVector, ConfigHelper.KeySize);
}

public static string DecryptData(string decryptText)
{
    return EncryptionHelper.DecryptData(decryptText, ConfigHelper.PassPhrase, ConfigHelper.SaltValue, ConfigHelper.HashAlgorithm, ConfigHelper.PasswordIterations, ConfigHelper.InitVector, ConfigHelper.KeySize);
}

Затем у меня было это в файле конфигурации ...

<add key="passPhrase" value=""/>
<add key="saltValue" value=""/>
<add key="hashAlgorithm" value="SHA1"/>
<add key="passwordIterations" value="5"/>
<add key="initVector" value=""/>
<add key="keySize" value="256"/>