EntityFrameworkCore.DataEncryption

EntityFrameworkCore.DataEncryption is a Microsoft Entity Framework Core extension to add support of encrypted fields using built-in or custom encryption providers.

Disclaimer

This library has been developed initialy for a personal project of mine. It provides a simple way to encrypt column data.

I do not take responsability if you use this in a production environment and loose your encryption key.

How to install

Install the package from NuGet or from the Package Manager Console :

PM> Install-Package EntityFrameworkCore.DataEncryption

How to use

To use EntityFrameworkCore.DataEncryption, you will need to decorate your string properties of your entities with the [Encrypted] attribute and enable the encryption on the ModelBuilder.

To enable the encryption correctly, you will need to use an encryption provider, there is a list of the available providers:

Example with AesProvider

public class UserEntity
{
	public int Id { get; set; }
	
	[Encrypted]
	public string Username { get; set; }
	
	[Encrypted]
	public string Password { get; set; }
	
	public int Age { get; set; }
}

public class DatabaseContext : DbContext
{
	// Get key and IV from a Base64String or any other ways.
	// You can generate a key and IV using "AesProvider.GenerateKey()"
	private readonly byte[] _encryptionKey = ...; 
	private readonly byte[] _encryptionIV = ...;
	private readonly IEncryptionProvider _provider;

	public DbSet<UserEntity> Users { get; set; }
	
	public DatabaseContext(DbContextOptions options)
		: base(options)
	{
		this._provider = new AesProvider(this._encryptionKey, this._encryptionIV);
	}
	
	protected override void OnModelCreating(ModelBuilder modelBuilder)
	{
		modelBuilder.UseEncryption(this._provider);
	}
}

The code bellow creates a new AesEncryption provider and gives it to the current model. It will encrypt every string fields of your model that has the [Encrypted] attribute when saving changes to database. As for the decrypt process, it will be done when reading the DbSet<T> of your DbContext.

Create an encryption provider

EntityFrameworkCore.DataEncryption gives the possibility to create your own encryption providers. To do so, create a new class and make it inherit from IEncryptionProvider. You will need to implement the Encrypt(string) and Decrypt(string) methods.

public class MyCustomEncryptionProvider : IEncryptionProvider
{
	public string Encrypt(string dataToEncrypt)
	{
		// Encrypt data and return as Base64 string
	}
	
	public string Decrypt(string dataToDecrypt)
	{
		// Decrypt a Base64 string to plain string
	}
}

To use it, simply create a new MyCustomEncryptionProvider in your DbContext and pass it to the UseEncryption method:

public class DatabaseContext : DbContext
{
	private readonly IEncryptionProvider _provider;

	public DatabaseContext(DbContextOptions options)
		: base(options)
	{
		this._provider = new MyCustomEncryptionProvider();
	}

	protected override void OnModelCreating(ModelBuilder modelBuilder)
	{
		modelBuilder.UseEncryption(this._provider);
	}
}

Important notes

AES Provider structure

The following section describes how encrypted fields using the built-in AES provider encrypts data.

For each encrypted field, the provider generates a new IV with a length of 16 bytes. These 16 bytes are written at the begining of the CryptoStream followed by the actual input to encrypt.

Similarly, for reading, the provider reads the first 16 bytes from the input data converted as a byte[] to retrieve the initialization vector and then read the encrypted content.

For more information, checkout the AesProvider class.