5-improve-encrypted-storage (#6)

Added the use of DEK's for encryption of secrets. Both the KEK's and DEK's are stored in a way that you can have multiple key of which one is active. But the others are still available for decrypting. This allows for implementing key rotation.

Co-authored-by: eelke <eelke@eelkeklein.nl>
Co-authored-by: Eelke76 <31384324+Eelke76@users.noreply.github.com>
Reviewed-on: #6

IdentityShroud.Core.Tests/Services/EncryptionTests.cs

@@ -0,0 +1,30 @@
+using IdentityShroud.Core.Security;
+using IdentityShroud.Core.Services;
+
+namespace IdentityShroud.Core.Tests.Services;
+
+public class EncryptionTests
+{
+    [Fact]
+    public void DecodeV1_Success()
+    {
+        // When introducing a new version we need version specific tests to 
+        // make sure decoding of legacy data still works.
+        
+        // setup
+        byte[] cipher =
+        [
+            1, 198, 55, 58, 56, 110, 238, 59, 158, 214, 85, 241, 26, 44, 140, 229, 128, 111, 167, 154, 160, 177, 152,
+            193, 74, 4, 235, 82, 207, 87, 32, 10, 239, 4, 246, 25, 21, 249, 25, 59, 160, 101
+        ];
+        byte[] keyValue = Convert.FromBase64String("IGd9yUMusjNW0ezv8ink3QWlAHKFH45d21LyrbJTokw=");
+        
+        // act
+        byte[] result = Encryption.Decrypt(cipher, keyValue);
+
+        // verify
+        Assert.Equal("Hello, World!"u8, result);
+    }
+
+    
+}