 <p>ok, I got it working consistently between the two accounts and the key was to set the UseMachineKeyStore flag.</p> <pre><code>private static RSACryptoServiceProvider CreateRsaCypher(string containerName = DefaultContainerName) { // Create the CspParameters object and set the key container // name used to store the RSA key pair. CspParameters cp = new CspParameters(); cp.KeyContainerName = containerName; cp.Flags = CspProviderFlags.UseExistingKey | CspProviderFlags.UseMachineKeyStore; // Create a new instance of RSACryptoServiceProvider that accesses // the key container MyKeyContainerName. return new RSACryptoServiceProvider(cp); } </code></pre>