Question

I am using the RSACryptoServiceProvider like this…

 private byte[] RSAEncrypt(byte[] DataToEncrypt, string ContainerName, bool DoOAEPPadding)
    {
        try
        {
            byte[] encryptedData;

            // Create a new instance of CspParameters.  Pass
            // 13 to specify a DSA container or 1 to specify
            // an RSA container.  The default is 1.
            CspParameters cspParams = new CspParameters();

            // Specify the container name using the passed variable.
            cspParams.KeyContainerName = ContainerName;

            cspParams.Flags = CspProviderFlags.UseDefaultKeyContainer;

            //Create a new instance of RSACryptoServiceProvider.
            using (RSACryptoServiceProvider RSA = new RSACryptoServiceProvider(cspParams))
            {
                //Encrypt the passed byte array and specify OAEP padding.  
                //OAEP padding is only available on Microsoft Windows XP or
                //later.  

                encryptedData = RSA.Encrypt(DataToEncrypt, DoOAEPPadding);
            }
            return encryptedData;
        }
        //Catch and display a CryptographicException  
        //to the console.
        catch (CryptographicException ex)
        {
            sl.Write(ex, MessageType.Error);
            throw;                
        }
    }

I then try to decrypt the data after turning off my Outlook Plugin Windows Form application and turning it back on which is what is using this peice of code. The decrypt code looks like this…

private byte[] RSAEncrypt(byte[] DataToEncrypt, string ContainerName, bool DoOAEPPadding)
    {
        try
        {
            byte[] encryptedData;

            // Create a new instance of CspParameters.  Pass
            // 13 to specify a DSA container or 1 to specify
            // an RSA container.  The default is 1.
            CspParameters cspParams = new CspParameters();

            // Specify the container name using the passed variable.
            cspParams.KeyContainerName = ContainerName;

            cspParams.Flags = CspProviderFlags.UseDefaultKeyContainer;

            //Create a new instance of RSACryptoServiceProvider.
            using (RSACryptoServiceProvider RSA = new RSACryptoServiceProvider(cspParams))
            {
                //Encrypt the passed byte array and specify OAEP padding.  
                //OAEP padding is only available on Microsoft Windows XP or
                //later.  

                encryptedData = RSA.Encrypt(DataToEncrypt, DoOAEPPadding);
            }
            return encryptedData;
        }
        //Catch and display a CryptographicException  
        //to the console.
        catch (CryptographicException ex)
        {
            sl.Write(ex, MessageType.Error);
            throw;                
        }
    }    

Works great until something comes up that I can not put my finger on. I don’t know if it is like the date changes or what. What happens is that I try to decrypt the data and I get a “bad data” error. Now again it works great until some elapsed period of time, or turning off the app, or the user logging off. I just don’t know and can’t determine what causes it. The moment I blow away the encrypted data which comes from a text file and recreate it and decrypt it I have no problem. Even if I restart the application in between encrypting/saving to file and the reading from file/decrypting it will works great! Something happens and I just don’t know KeyContainers well enough to understand what could possibly make the CspParameters expire is my best guess?

Answer 1

I ended up using the CspParameters flag and instead of using the Users KeyContainer store I used the Machine KeyContainer Store.