How can i save files in the phone accessible by several apps?

Question

I try to develop several WP8 apps using the same credentials for all(same user and password).So if the user choose to change his credentials he does only once in one app and it will change for all. Until now i used Isolatedstorage to save the credentials(as shown below) but im wondering if the files would be accessible by all the apps...i guess they would not. So what solution do you have ?

thanks for your help

   public static void SaveToFile(byte[] Encryptedfile, string FileName)
    {
        using (var SaveApplicationFile = IsolatedStorageFile.GetUserStoreForApplication())
        {
            SaveApplicationFile.DeleteFile(FileName);
            using (IsolatedStorageFileStream fileAsStream = new IsolatedStorageFileStream(FileName, System.IO.FileMode.Create, FileAccess.Write, SaveApplicationFile))
            {
                using (Stream writer = new StreamWriter(fileAsStream).BaseStream)
                {
                    writer.Write(Encryptedfile, 0, Encryptedfile.Length);
                }

            }
        }
    }

Answer 1

You can't access IsolatedStorage of other App.
Nor you can't save on SD card.
Maybe consider using Skydrive or other exteral storage.
Another idea, I'm thinking about - maybe you can use MediaLibrary and Save Picture there. And use this picture as a container for some data - maybe using Steganography ;)