Encrypting SecureString to regular string

SecureStringencryption.cs

        /// <summary>
        /// Encrypts a SecureString to a regular string.
        /// </summary>
        /// <remarks>This is a draft that Im hoping to get comments on in http://stackoverflow.com/a/26202992/1187583</remarks>
        public static string EncryptSecureStringToRegularString(this SecureString secureString)
        {
            var pointer = IntPtr.Zero;
            try
            {
                var store = new X509Store(StoreName.My, StoreLocation.LocalMachine);
                store.Open(OpenFlags.ReadOnly | OpenFlags.OpenExistingOnly);
                var myRsa = (from X509Certificate2 x509 in store.Certificates where x509.FriendlyName == EngineSettings.Settings.CertificateFriendlyName select (RSACryptoServiceProvider)x509.PrivateKey).FirstOrDefault();

                pointer = Marshal.SecureStringToGlobalAllocUnicode(secureString);

                byte[] byteArray = Encoding.ASCII.GetBytes(Marshal.PtrToStringUni(pointer));

                return Encoding.ASCII.GetString(myRsa.Encrypt(byteArray, true));
            }
            finally
            {
                Marshal.ZeroFreeGlobalAllocUnicode(pointer);
            }
        }
        
        
        //And then the usage
        var encodedString = secureString.EncryptSecureStringToRegularString();