Skip to main content

Azure Storage - Client Side Encryption

A few days ago, client-side encryption for Azure Storage was announced. In this post we will take a look over this feature.

First of all, you should know that the encryption/decryption takes place on client side. This means, that the content will be already encryption when it will arrive on Azure. This encryption technique is called Envelop Technique. It is very useful when you want to add another security layer over your data.
Out of the box, there are client library for .NET (including Windows Phone). For other languages, like Java is not yet supported, but because the encryption algorithm is a well know one, you may be able to implement it on other platforms also.

The encryption algorithm that is used by client library is AES (Advanced Encryption Standard). It is important to know that the encryption keys are generated by the client library. And is NEVER stored in Azure Storage. The encryption key should be stored in a different location. This library is full integration with Key Vault Service, that allow us to persist the keys in a safe location.

The encryption mechanism is not complicated, but is very useful. You don't need to encrypt by yourself, using different libraries and orchestrate all the activities. From a developer perspective, the life is more simple and the chances to introduce a bug are reduced.

There are some small things that we should consider when using this library.
First thing is related to blobs. All reads and writes operations needs to be made on the entire blob content. This means that we should not upload encrypted content using PutBlock. All the time, we should use DownloadToXXX, BlobReadStreamXXX, UploadFromXXX and OpenWriteXXX.
This is necessary because each time when you upload content, a new IV (Initialization Vector) is generated. This information is stored in blob metadata and will be used during decryption.
A similar situation is on Azure Tables. We have full support for action like Insert and Replace, but Merging is not supported.
The interesting thing is when we are using Azure Queue and we want to encrypt content. In this situation, the encryption information (IV and a random CEK) are added to each message. This means that we can work separately with each message. Take into account that for each message, the message body will contain also the IV and CEK. Because of this the size of the message and queue will be bigger.

In the below diagram, we can see where the encryption metadata are stored (IV, CEK).

If you want to enforce to encryption all the content that is stored in Azure Storage, you can set the 'RequireEncryption' to TRUE. In this way, you will enforce the client to encrypt all the content that is send. If you want to take a look over the implementation you can see the source code on GitHub -


Popular posts from this blog

ADO.NET provider with invariant name 'System.Data.SqlClient' could not be loaded

Today blog post will be started with the following error when running DB tests on the CI machine:
threw exception: System.InvalidOperationException: The Entity Framework provider type 'System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer' registered in the application config file for the ADO.NET provider with invariant name 'System.Data.SqlClient' could not be loaded. Make sure that the assembly-qualified name is used and that the assembly is available to the running application. See for more information. at System.Data.Entity.Infrastructure.DependencyResolution.ProviderServicesFactory.GetInstance(String providerTypeName, String providerInvariantName) This error happened only on the Continuous Integration machine. On the devs machines, everything has fine. The classic problem – on my machine it’s working. The CI has the following configuration:

TeamCity.NET 4.51EF 6.0.2VS2013
It seems that there …

GET call of REST API that contains '/'-slash character in the value of a parameter

Let’s assume that we have the following scenario: I have a public HTTP endpoint and I need to post some content using GET command. One of the parameters contains special characters like “\” and “/”. If the endpoint is an ApiController than you may have problems if you encode the parameter using the http encoder.
using (var httpClient = new HttpClient()) { httpClient.BaseAddress = baseUrl; Task<HttpResponseMessage> response = httpClient.GetAsync(string.Format("api/foo/{0}", "qwert/qwerqwer"))); response.Wait(); response.Result.EnsureSuccessStatusCode(); } One possible solution would be to encode the query parameter using UrlTokenEncode method of HttpServerUtility class and GetBytes method ofUTF8. In this way you would get the array of bytes of the parameter and encode them as a url token.
The following code show to you how you could write the encode and decode methods.

Entity Framework (EF) TransactionScope vs Database.BeginTransaction

In today blog post we will talk a little about a new feature that is available on EF6+ related to Transactions.
Until now, when we had to use transaction we used ‘TransactionScope’. It works great and I would say that is something that is now in our blood.
using (var scope = new TransactionScope(TransactionScopeOption.Required)) { using (SqlConnection conn = new SqlConnection("...")) { conn.Open(); SqlCommand sqlCommand = new SqlCommand(); sqlCommand.Connection = conn; sqlCommand.CommandText = ... sqlCommand.ExecuteNonQuery(); ... } scope.Complete(); } Starting with EF6.0 we have a new way to work with transactions. The new approach is based on Database.BeginTransaction(), Database.Rollback(), Database.Commit(). Yes, no more TransactionScope.
In the followi…