Support rotation of master key.

The EncryptionService now loads a set of keys and uses the active one to encrypt and selects key based on keyid during decryption. Introduced EncryptedValue to hold keyId and encrypted data.

(There are no intermeddiate keys yet)

.github/workflows/ci.yml

@@ -0,0 +1,71 @@
+name: CI
+
+on:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup .NET
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: '10.0.x'
+
+      - name: Cache NuGet packages
+        uses: actions/cache@v4
+        with:
+          path: ~/.nuget/packages
+          key: ${{ runner.os }}-nuget-${{ hashFiles('**/*.csproj') }}
+          restore-keys: |
+            ${{ runner.os }}-nuget-
+
+      - name: Cache Docker image (postgres)
+        id: docker-cache
+        uses: actions/cache@v4
+        with:
+          path: /tmp/docker-postgres.tar
+          key: ${{ runner.os }}-docker-postgres-18.1
+
+      - name: Load cached postgres image or pull
+        run: |
+          if [ -f /tmp/docker-postgres.tar ]; then
+            docker load -i /tmp/docker-postgres.tar
+          else
+            docker pull postgres:18.1
+            docker save postgres:18.1 -o /tmp/docker-postgres.tar
+          fi
+
+      - name: Restore dependencies
+        run: dotnet restore
+
+      - name: Build
+        run: dotnet build --no-restore --configuration Release
+
+      - name: Test with coverage
+        run: |
+          dotnet test --no-build --configuration Release \
+            --collect:"XPlat Code Coverage" \
+            --results-directory ./coverage \
+            -- DataCollectionRunSettings.DataCollectors.DataCollector.Configuration.Format=cobertura
+
+      - name: Code Coverage Report
+        uses: irongut/CodeCoverageSummary@v1.3.0
+        with:
+          filename: coverage/**/coverage.cobertura.xml
+          badge: true
+          format: markdown
+          output: both
+
+      - name: Upload coverage artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: coverage-report
+          path: ./coverage/**/coverage.cobertura.xml
+          retention-days: 7

IdentityShroud.Api.Tests/Apis/ClientApiTests.cs

@@ -0,0 +1,179 @@
+using System.Net;
+using System.Net.Http.Json;
+using IdentityShroud.Core;
+using IdentityShroud.Core.Model;
+using IdentityShroud.Core.Tests.Fixtures;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace IdentityShroud.Api.Tests.Apis;
+
+public class ClientApiTests : IClassFixture<ApplicationFactory>
+{
+    private readonly ApplicationFactory _factory;
+
+    public ClientApiTests(ApplicationFactory factory)
+    {
+        _factory = factory;
+
+        using var scope = _factory.Services.CreateScope();
+        var db = scope.ServiceProvider.GetRequiredService<Db>();
+        if (!db.Database.EnsureCreated())
+        {
+            db.Database.ExecuteSqlRaw("TRUNCATE realm CASCADE;");
+        }
+    }
+
+    [Theory]
+    [InlineData(null, false, "ClientId")]
+    [InlineData("", false, "ClientId")]
+    [InlineData("my-client", true, "")]
+    public async Task Create_Validation(string? clientId, bool succeeds, string fieldName)
+    {
+        // setup
+        Realm realm = await CreateRealmAsync("test-realm", "Test Realm");
+
+        var client = _factory.CreateClient();
+
+        // act
+        var response = await client.PostAsync(
+            $"/api/v1/realms/{realm.Id}/clients",
+            JsonContent.Create(new { ClientId = clientId }),
+            TestContext.Current.CancellationToken);
+
+#if DEBUG
+        string contents = await response.Content.ReadAsStringAsync(TestContext.Current.CancellationToken);
+#endif
+
+        if (succeeds)
+        {
+            Assert.Equal(HttpStatusCode.Created, response.StatusCode);
+        }
+        else
+        {
+            Assert.Equal(HttpStatusCode.BadRequest, response.StatusCode);
+            var problemDetails =
+                await response.Content.ReadFromJsonAsync<ValidationProblemDetails>(
+                    TestContext.Current.CancellationToken);
+
+            Assert.Contains(problemDetails!.Errors, e => e.Key == fieldName);
+        }
+    }
+
+    [Fact]
+    public async Task Create_Success_ReturnsCreatedWithLocation()
+    {
+        // setup
+        Realm realm = await CreateRealmAsync("create-realm", "Create Realm");
+
+        var client = _factory.CreateClient();
+
+        // act
+        var response = await client.PostAsync(
+            $"/api/v1/realms/{realm.Id}/clients",
+            JsonContent.Create(new { ClientId = "new-client", Name = "New Client" }),
+            TestContext.Current.CancellationToken);
+
+#if DEBUG
+        string contents = await response.Content.ReadAsStringAsync(TestContext.Current.CancellationToken);
+#endif
+
+        // verify
+        Assert.Equal(HttpStatusCode.Created, response.StatusCode);
+
+        var body = await response.Content.ReadFromJsonAsync<ClientCreateReponse>(
+            TestContext.Current.CancellationToken);
+
+        Assert.NotNull(body);
+        Assert.Equal("new-client", body.ClientId);
+        Assert.True(body.Id > 0);
+    }
+
+    [Fact]
+    public async Task Create_UnknownRealm_ReturnsNotFound()
+    {
+        var client = _factory.CreateClient();
+
+        var response = await client.PostAsync(
+            $"/api/v1/realms/{Guid.NewGuid()}/clients",
+            JsonContent.Create(new { ClientId = "some-client" }),
+            TestContext.Current.CancellationToken);
+
+        Assert.Equal(HttpStatusCode.NotFound, response.StatusCode);
+    }
+
+    [Fact]
+    public async Task Get_Success()
+    {
+        // setup
+        Realm realm = await CreateRealmAsync("get-realm", "Get Realm");
+        Client dbClient = await CreateClientAsync(realm, "get-client", "Get Client");
+
+        var httpClient = _factory.CreateClient();
+
+        // act
+        var response = await httpClient.GetAsync(
+            $"/api/v1/realms/{realm.Id}/clients/{dbClient.Id}",
+            TestContext.Current.CancellationToken);
+
+#if DEBUG
+        string contents = await response.Content.ReadAsStringAsync(TestContext.Current.CancellationToken);
+#endif
+
+        // verify
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+
+        var body = await response.Content.ReadFromJsonAsync<ClientRepresentation>(
+            TestContext.Current.CancellationToken);
+
+        Assert.NotNull(body);
+        Assert.Equal(dbClient.Id, body.Id);
+        Assert.Equal("get-client", body.ClientId);
+        Assert.Equal("Get Client", body.Name);
+        Assert.Equal(realm.Id, body.RealmId);
+    }
+
+    [Fact]
+    public async Task Get_UnknownClient_ReturnsNotFound()
+    {
+        // setup
+        Realm realm = await CreateRealmAsync("notfound-realm", "NotFound Realm");
+
+        var httpClient = _factory.CreateClient();
+
+        // act
+        var response = await httpClient.GetAsync(
+            $"/api/v1/realms/{realm.Id}/clients/99999",
+            TestContext.Current.CancellationToken);
+
+        // verify
+        Assert.Equal(HttpStatusCode.NotFound, response.StatusCode);
+    }
+
+    private async Task<Realm> CreateRealmAsync(string slug, string name)
+    {
+        using var scope = _factory.Services.CreateScope();
+        var db = scope.ServiceProvider.GetRequiredService<Db>();
+        var realm = new Realm { Slug = slug, Name = name };
+        db.Realms.Add(realm);
+        await db.SaveChangesAsync(TestContext.Current.CancellationToken);
+        return realm;
+    }
+
+    private async Task<Client> CreateClientAsync(Realm realm, string clientId, string? name = null)
+    {
+        using var scope = _factory.Services.CreateScope();
+        var db = scope.ServiceProvider.GetRequiredService<Db>();
+        var client = new Client
+        {
+            RealmId = realm.Id,
+            ClientId = clientId,
+            Name = name,
+            CreatedAt = DateTime.UtcNow,
+        };
+        db.Clients.Add(client);
+        await db.SaveChangesAsync(TestContext.Current.CancellationToken);
+        return client;
+    }
+}

IdentityShroud.Api.Tests/Apis/RealmApisTests.cs

@@ -114,7 +114,7 @@ public class RealmApisTests : IClassFixture<ApplicationFactory>
     {
         // act
         var client = _factory.CreateClient();
-        var response = await client.GetAsync("/realms/bar/.well-known/openid-configuration",
+        var response = await client.GetAsync($"/realms/{slug}/.well-known/openid-configuration",
             TestContext.Current.CancellationToken);
         
         // verify
@@ -130,11 +130,13 @@ public class RealmApisTests : IClassFixture<ApplicationFactory>
         using var rsa = RSA.Create(2048);
         RSAParameters parameters = rsa.ExportParameters(includePrivateParameters: false);
 
-        RealmKey realmKey = new(
-            Guid.NewGuid(),
-            "RSA",
-            encryptionService.Encrypt(rsa.ExportPkcs8PrivateKey()),
-            DateTime.UtcNow);
+        RealmKey realmKey = new()
+        {
+            Id = Guid.NewGuid(),
+            KeyType = "RSA",
+            Key = encryptionService.Encrypt(rsa.ExportPkcs8PrivateKey()),
+            CreatedAt = DateTime.UtcNow,
+        };
 
         await ScopedContextAsync(async db =>
         {

IdentityShroud.Api.Tests/Fixtures/ApplicationFactory.cs

@@ -1,11 +1,6 @@
-using IdentityShroud.Core.Services;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Mvc.Testing;
-using Microsoft.EntityFrameworkCore.Infrastructure;
 using Microsoft.Extensions.Configuration;
-using Microsoft.Extensions.DependencyInjection;
-using Microsoft.VisualStudio.TestPlatform.TestHost;
-using Npgsql;
 using Testcontainers.PostgreSql;
 
 namespace IdentityShroud.Core.Tests.Fixtures;
@@ -33,7 +28,10 @@ public class ApplicationFactory : WebApplicationFactory<Program>, IAsyncLifetime
                 new Dictionary<string, string?>
                 {
                     ["Db:ConnectionString"] = _postgresqlServer.GetConnectionString(),
-                    ["Encryption:Master"] = "GVd07qW0frRX9quPX/X62L88BeRR7+IzgRJHtG7ZzHw=",
+                    ["secrets:master:0:Id"] = "key1",
+                    ["secrets:master:0:Active"] = "true",
+                    ["secrets:master:0:Algorithm"] = "AES",
+                    ["secrets:master:0:Key"] = "GVd07qW0frRX9quPX/X62L88BeRR7+IzgRJHtG7ZzHw=",
                 });
         });
         

IdentityShroud.Api.Tests/Mappers/KeyMapperTests.cs

@@ -1,17 +0,0 @@
-using IdentityShroud.Api.Mappers;
-using IdentityShroud.Core.Contracts;
-using IdentityShroud.Core.Messages;
-using IdentityShroud.TestUtils.Substitutes;
-using Microsoft.AspNetCore.WebUtilities;
-
-namespace IdentityShroud.Api.Tests.Mappers;
-
-// public class KeyMapperTests
-// {
-//     private readonly IEncryptionService _encryptionService = EncryptionServiceSubstitute.CreatePassthrough();
-//
-//     [Fact]
-//     public void Test()
-//     {
-//     }
-// }

IdentityShroud.Api.Tests/Mappers/KeyServiceTests.cs

@@ -21,12 +21,12 @@ public class KeyServiceTests
 
         RSAParameters parameters = rsa.ExportParameters(includePrivateParameters: false);
         
-        RealmKey realmKey = new(
-            new("60bb79cf-4bac-4521-87f2-ac87cc15541f"),
-            "RSA",
-            rsa.ExportPkcs8PrivateKey(),
-            DateTime.UtcNow)
+        RealmKey realmKey = new()
         {
+            Id = new("60bb79cf-4bac-4521-87f2-ac87cc15541f"),
+            KeyType = "RSA",
+            Key = new("", rsa.ExportPkcs8PrivateKey()),
+            CreatedAt = DateTime.UtcNow,
             Priority = 10,
         };
         
@@ -34,6 +34,7 @@ public class KeyServiceTests
         KeyService sut = new(_encryptionService, new KeyProviderFactory(), new ClockService());
         var jwk = sut.CreateJsonWebKey(realmKey);
 
+        Assert.NotNull(jwk);
         Assert.Equal("RSA", jwk.KeyType);
         Assert.Equal(realmKey.Id.ToString(), jwk.KeyId);
         Assert.Equal("sig", jwk.Use);

IdentityShroud.Api/Apis/ClientApi.cs

@@ -1,14 +1,14 @@
 using FluentResults;
+using IdentityShroud.Api.Mappers;
 using IdentityShroud.Core.Contracts;
-using IdentityShroud.Core.Messages.Realm;
 using IdentityShroud.Core.Model;
-using IdentityShroud.Core.Services;
 using Microsoft.AspNetCore.Http.HttpResults;
 using Microsoft.AspNetCore.Mvc;
 
 namespace IdentityShroud.Api;
 
 
+
 public record ClientCreateReponse(int Id, string ClientId);
 
 /// <summary>
@@ -34,13 +34,18 @@ public static class ClientApi
             .WithName(ClientGetRouteName);
     }
 
-    private static Task ClientGet(HttpContext context)
+    private static Ok<ClientRepresentation> ClientGet(
+        Guid realmId,
+        int clientId,
+        HttpContext context)
     {
-        throw new NotImplementedException();
+        Client client = (Client)context.Items["ClientEntity"]!;
+        return TypedResults.Ok(new ClientMapper().ToDto(client));
     }
 
     private static async Task<Results<CreatedAtRoute<ClientCreateReponse>, InternalServerError>>
         ClientCreate(
+            Guid realmId,
             ClientCreateRequest request, 
             [FromServices] IClientService service,
             HttpContext context,
@@ -64,6 +69,5 @@ public static class ClientApi
                 ["realmId"] = realm.Id,
                 ["clientId"] = client.Id, 
             });
-        throw new NotImplementedException();
     }
 }

IdentityShroud.Api/Apis/Dto/ClientRepresentation.cs

@@ -0,0 +1,16 @@
+namespace IdentityShroud.Api;
+
+public record ClientRepresentation
+{
+    public int Id { get; set; }
+    public Guid RealmId { get; set; }
+    public required string ClientId { get; set; }
+    public string? Name { get; set; }
+    public string? Description { get; set; }
+    
+    public string? SignatureAlgorithm { get; set; }
+    
+    public bool AllowClientCredentialsFlow { get; set; } = false;
+    
+    public required DateTime CreatedAt { get; set; }
+}

IdentityShroud.Api/Apis/Filters/ClientIdValidationFilter.cs

@@ -7,8 +7,9 @@ public class ClientIdValidationFilter(IClientService clientService) : IEndpointF
 {
     public async ValueTask<object?> InvokeAsync(EndpointFilterInvocationContext context, EndpointFilterDelegate next)
     {
+        Guid realmId = context.Arguments.OfType<Guid>().First();
         int id = context.Arguments.OfType<int>().First();
-        Client? client = await clientService.FindById(id, context.HttpContext.RequestAborted);
+        Client? client = await clientService.FindById(realmId, id, context.HttpContext.RequestAborted);
         if (client is null)
         {
             return Results.NotFound();

IdentityShroud.Api/Apis/Filters/RealmSlugValidationFilter.cs

@@ -1,6 +1,5 @@
 using IdentityShroud.Core.Contracts;
 using IdentityShroud.Core.Model;
-using IdentityShroud.Core.Services;
 
 namespace IdentityShroud.Api;
 

IdentityShroud.Api/Apis/Mappers/ClientMapper.cs

@@ -0,0 +1,11 @@
+using IdentityShroud.Core.Model;
+using Riok.Mapperly.Abstractions;
+
+namespace IdentityShroud.Api.Mappers;
+
+[Mapper]
+public partial class ClientMapper
+{
+    [MapperIgnoreSource(nameof(Client.Secrets))]
+    public partial ClientRepresentation ToDto(Client client);
+}

IdentityShroud.Api/Apis/Mappers/KeyMapper.cs

@@ -1,9 +1,6 @@
-using System.Security.Cryptography;
 using IdentityShroud.Core.Contracts;
 using IdentityShroud.Core.Messages;
 using IdentityShroud.Core.Model;
-using IdentityShroud.Core.Security;
-using Microsoft.AspNetCore.WebUtilities;
 
 namespace IdentityShroud.Api.Mappers;
 

IdentityShroud.Api/Apis/Validation/ClientCreateRequestValidator.cs

@@ -0,0 +1,22 @@
+using FluentValidation;
+using IdentityShroud.Core.Contracts;
+
+namespace IdentityShroud.Api;
+
+public class ClientCreateRequestValidator : AbstractValidator<ClientCreateRequest>
+{
+    // most of standard ascii minus the control characters and space 
+    private const string ClientIdPattern = "^[\x21-\x7E]+";
+
+    private string[] AllowedAlgorithms = [ "RS256", "ES256" ];
+    
+    public ClientCreateRequestValidator()
+    {
+        RuleFor(e => e.ClientId).NotEmpty().MaximumLength(40).Matches(ClientIdPattern);
+        RuleFor(e => e.Name).MaximumLength(80);
+        RuleFor(e => e.Description).MaximumLength(2048);
+        RuleFor(e => e.SignatureAlgorithm)
+            .Must(v => v is null || AllowedAlgorithms.Contains(v))
+            .WithMessage($"SignatureAlgorithm must be one of {string.Join(", ", AllowedAlgorithms)} or null");
+    }
+}

IdentityShroud.Api/AppJsonSerializerContext.cs

@@ -1,7 +1,6 @@
 using System.Text.Json.Serialization;
 using IdentityShroud.Core.Messages;
 using IdentityShroud.Core.Messages.Realm;
-using Microsoft.Extensions.Diagnostics.HealthChecks;
 
 [JsonSerializable(typeof(OpenIdConfiguration))]
 [JsonSerializable(typeof(RealmCreateRequest))]

IdentityShroud.Api/IdentityShroud.Api.csproj

@@ -17,7 +17,7 @@
     <ItemGroup>
         <PackageReference Include="FluentValidation.DependencyInjectionExtensions" Version="12.1.1" />
         <PackageReference Include="Microsoft.AspNetCore.OpenApi" Version="10.0.0"/>
-        <PackageReference Include="Microsoft.Extensions.Configuration.Binder" Version="10.0.2" />
+        <PackageReference Include="Riok.Mapperly" Version="4.3.1" />
         <PackageReference Include="Serilog" Version="4.3.0" />
         <PackageReference Include="Serilog.AspNetCore" Version="10.0.0" />
         <PackageReference Include="Serilog.Expressions" Version="5.0.0" />

IdentityShroud.Core.Tests/Fixtures/DbFixture.cs

@@ -1,5 +1,4 @@
-using DotNet.Testcontainers.Containers;
-using Microsoft.Extensions.Logging.Abstractions;
+using Microsoft.Extensions.Logging.Abstractions;
 using Microsoft.Extensions.Options;
 using Npgsql;
 using Testcontainers.PostgreSql;

IdentityShroud.Core.Tests/IdentityShroud.Core.Tests.csproj

@@ -30,8 +30,4 @@
       <ProjectReference Include="..\IdentityShroud.TestUtils\IdentityShroud.TestUtils.csproj" />
     </ItemGroup>
 
-    <ItemGroup>
-      <Folder Include="Model\" />
-    </ItemGroup>
-
 </Project>

IdentityShroud.Core.Tests/JwtSignatureGeneratorTests.cs

@@ -72,8 +72,8 @@ public class JwtSignatureGeneratorTests
         var rsa = RSA.Create();
         var parameters = new RSAParameters
         {
-            Modulus = WebEncoders.Base64UrlDecode(jwk.Modulus),
-            Exponent = WebEncoders.Base64UrlDecode(jwk.Exponent)
+            Modulus = WebEncoders.Base64UrlDecode(jwk.Modulus!),
+            Exponent = WebEncoders.Base64UrlDecode(jwk.Exponent!)
         };
         
         rsa.ImportParameters(parameters);

IdentityShroud.Core.Tests/Security/AesGcmHelperTests.cs

@@ -1,21 +0,0 @@
-using System.Security.Cryptography;
-using System.Text;
-using IdentityShroud.Core.Security;
-
-namespace IdentityShroud.Core.Tests.Security;
-
-public class AesGcmHelperTests
-{
-    [Fact]
-    public void EncryptDecryptCycleWorks()
-    {
-        string input = "Hello, world!";
-
-        var encryptionKey = RandomNumberGenerator.GetBytes(32);
-
-        var cypher = AesGcmHelper.EncryptAesGcm(Encoding.UTF8.GetBytes(input), encryptionKey);
-        var output = AesGcmHelper.DecryptAesGcm(cypher, encryptionKey);
-        
-        Assert.Equal(input, Encoding.UTF8.GetString(output));
-    }
-}

IdentityShroud.Core.Tests/Security/ConfigurationSecretProviderTests.cs

@@ -0,0 +1,61 @@
+using System.Text;
+using IdentityShroud.Core.Security;
+using Microsoft.Extensions.Configuration;
+
+namespace IdentityShroud.Core.Tests.Security;
+
+public class ConfigurationSecretProviderTests
+{
+    private static IConfiguration BuildConfigFromJson(string json)
+    {
+        // Convert the JSON string into a stream that the config builder can read.
+        var jsonBytes = Encoding.UTF8.GetBytes(json);
+        using var stream = new MemoryStream(jsonBytes);
+
+        // Build the configuration just like the real app does, but from the stream.
+        var config = new ConfigurationBuilder()
+            .AddJsonStream(stream)   // <-- reads from the in‑memory JSON
+            .Build();
+
+        return config;
+    }
+
+    [Fact]
+    public void Test()
+    {
+        string jsonConfig = """
+            {
+                "secrets": {
+                    "master": [
+                        {
+                            "Id": "first",
+                            "Active": true,
+                            "Algorithm": "AES",
+                            "Key": "yoQ4W7EaNjo7s3FBYkWo5BLyX1BnLyWd7BlSaDIrkzo="
+                        },
+                        {
+                            "Id": "second",
+                            "Active": false,
+                            "Algorithm": "AES",
+                            "Key": "YSWK6vTJXCJOGLpCo+TtZ6anKNzvA1VT2xXLHbmq4M0="
+                        }
+                    ]    
+                }
+            }
+            """;
+        
+
+        ConfigurationSecretProvider sut = new(BuildConfigFromJson(jsonConfig));
+
+        var keys = sut.GetKeys("master");
+
+        Assert.Equal(2, keys.Length);
+        var active = keys.Single(k => k.Active);
+        Assert.Equal("first", active.Id);
+        Assert.Equal("AES", active.Algorithm);
+        Assert.Equal(Convert.FromBase64String("yoQ4W7EaNjo7s3FBYkWo5BLyX1BnLyWd7BlSaDIrkzo="), active.Key);
+
+        var inactive = keys.Single(k => !k.Active);
+        Assert.Equal("second", inactive.Id);
+    }
+}

IdentityShroud.Core.Tests/Services/ClientServiceTests.cs

@@ -108,7 +108,7 @@ public class ClientServiceTests : IClassFixture<DbFixture>
         await using var actContext = _dbFixture.CreateDbContext();
         // Act
         ClientService sut = new(actContext, _encryptionService, _clock);
-        Client? result = await sut.GetByClientId(clientId, TestContext.Current.CancellationToken);
+        Client? result = await sut.GetByClientId(_realmId, clientId, TestContext.Current.CancellationToken);
 
         // Verify
         if (shouldFind)
@@ -143,7 +143,7 @@ public class ClientServiceTests : IClassFixture<DbFixture>
         await using var actContext = _dbFixture.CreateDbContext();
         // Act
         ClientService sut = new(actContext, _encryptionService, _clock);
-        Client? result = await sut.FindById(searchId, TestContext.Current.CancellationToken);
+        Client? result = await sut.FindById(_realmId, searchId, TestContext.Current.CancellationToken);
 
         // Verify
         if (shouldFind)

IdentityShroud.Core.Tests/Services/EncryptionServiceTests.cs

@@ -1,4 +1,3 @@
-using System.Security.Cryptography;
 using IdentityShroud.Core.Contracts;
 using IdentityShroud.Core.Services;
 
@@ -9,18 +8,139 @@ public class EncryptionServiceTests
     [Fact]
     public void RoundtripWorks()
     {
-        // setup
-        string key = Convert.ToBase64String(RandomNumberGenerator.GetBytes(32));
-        var secretProvider = Substitute.For<ISecretProvider>();
-        secretProvider.GetSecret("Master").Returns(key);
+        // Note this code will tend to only test the latest verion.
 
-        EncryptionService sut = new(secretProvider);
-        byte[] input = RandomNumberGenerator.GetBytes(16);
+        // setup
+        byte[] keyValue = Convert.FromBase64String("IGd9yUMusjNW0ezv8ink3QWlAHKFH45d21LyrbJTokw=");
+        var secretProvider = Substitute.For<ISecretProvider>();
+        EncryptionKey[] keys =
+        [
+            new EncryptionKey("1", true, "AES", keyValue)
+        ];
+        secretProvider.GetKeys("master").Returns(keys);
+        
+            
+        ReadOnlySpan<byte> input = "Hello, World!"u8;
         
         // act
-        var cipher = sut.Encrypt(input);
-        var result = sut.Decrypt(cipher);
+        EncryptionService sut = new(secretProvider);
+        EncryptedValue cipher = sut.Encrypt(input.ToArray());
+        byte[] result = sut.Decrypt(cipher);
 
+        // verify
         Assert.Equal(input, result);
     }
+
+    [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
+        ];
+        EncryptedValue secret = new("kid", cipher);
+        
+        byte[] keyValue = Convert.FromBase64String("IGd9yUMusjNW0ezv8ink3QWlAHKFH45d21LyrbJTokw=");
+        var secretProvider = Substitute.For<ISecretProvider>();
+        EncryptionKey[] keys =
+        [
+            new EncryptionKey("kid", true, "AES", keyValue)
+        ];
+        secretProvider.GetKeys("master").Returns(keys);
+
+        // act
+        EncryptionService sut = new(secretProvider);
+        byte[] result = sut.Decrypt(secret);
+
+        // verify
+        Assert.Equal("Hello, World!"u8, result);
+    }
+
+    [Fact]
+    public void DetectsCorruptInput()
+    {
+        // When introducing a new version we need version specific tests to 
+        // make sure decoding of legacy data still works.
+        
+        // setup
+        byte[] cipher = // NOTE INCORRECT CIPHER DO NOT USE IN OTHER TESTS
+        [
+            1, 198, 55, 58, 56, 110, 238, 59, 158, 214, 85, 241, 26, 44, 140, 229, 128, 111, 167, 154, 160, 177, 152,
+            193, 75, 4, 235, 82, 207, 87, 32, 10, 239, 4, 246, 25, 21, 249, 25, 59, 160, 101
+        ];
+        EncryptedValue secret = new("kid", cipher);
+        
+        byte[] keyValue = Convert.FromBase64String("IGd9yUMusjNW0ezv8ink3QWlAHKFH45d21LyrbJTokw=");
+        var secretProvider = Substitute.For<ISecretProvider>();
+        EncryptionKey[] keys =
+        [
+            new EncryptionKey("kid", true, "AES", keyValue)
+        ];
+        secretProvider.GetKeys("master").Returns(keys);
+
+        // act
+        EncryptionService sut = new(secretProvider);
+        Assert.Throws<InvalidOperationException>(
+            () => sut.Decrypt(secret),
+            ex => ex.Message.Contains("Decryption failed") ? null : "Expected Decryption failed in message");
+    }
+
+    [Fact]
+    public void DecodeSelectsRightKey()
+    {
+        // The key is marked inactive also it is the second key
+        
+        // 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
+        ];
+        EncryptedValue secret = new("1", cipher);
+        
+        byte[] keyValue1 = Convert.FromBase64String("IGd9yUMusjNW0ezv8ink3QWlAHKFH45d21LyrbJTokw=");
+        byte[] keyValue2 = Convert.FromBase64String("Dat1RwRvuLX3wdKMMP4NwHdBl8tJJsKfp01qikyo8aw=");
+        var secretProvider = Substitute.For<ISecretProvider>();
+        EncryptionKey[] keys =
+        [
+            new EncryptionKey("2", true, "AES", keyValue2),
+            new EncryptionKey("1", false, "AES", keyValue1),
+        ];
+        secretProvider.GetKeys("master").Returns(keys);
+
+        // act
+        EncryptionService sut = new(secretProvider);
+        byte[] result = sut.Decrypt(secret);
+
+        // verify
+        Assert.Equal("Hello, World!"u8, result);
+    }
+    
+    [Fact]
+    public void EncryptionUsesActiveKey()
+    {
+        // setup
+        byte[] keyValue1 = Convert.FromBase64String("IGd9yUMusjNW0ezv8ink3QWlAHKFH45d21LyrbJTokw=");
+        byte[] keyValue2 = Convert.FromBase64String("Dat1RwRvuLX3wdKMMP4NwHdBl8tJJsKfp01qikyo8aw=");
+        var secretProvider = Substitute.For<ISecretProvider>();
+        EncryptionKey[] keys =
+        [
+            new EncryptionKey("1", false, "AES", keyValue1),
+            new EncryptionKey("2", true, "AES", keyValue2),
+        ];
+        secretProvider.GetKeys("master").Returns(keys);
+
+        ReadOnlySpan<byte> input = "Hello, World!"u8;
+        // act
+        EncryptionService sut = new(secretProvider);
+        EncryptedValue cipher = sut.Encrypt(input.ToArray());
+        
+        // Verify
+        Assert.Equal("2", cipher.KeyId);
+    }
 }

IdentityShroud.Core.Tests/Services/RealmServiceTests.cs

@@ -3,7 +3,6 @@ using IdentityShroud.Core.Model;
 using IdentityShroud.Core.Security.Keys;
 using IdentityShroud.Core.Services;
 using IdentityShroud.Core.Tests.Fixtures;
-using IdentityShroud.TestUtils.Substitutes;
 using Microsoft.EntityFrameworkCore;
 
 namespace IdentityShroud.Core.Tests.Services;
@@ -40,7 +39,13 @@ public class RealmServiceTests : IClassFixture<DbFixture>
         await using (var db = _dbFixture.CreateDbContext())
         {
             _keyService.CreateKey(Arg.Any<KeyPolicy>())
-                .Returns(new RealmKey(Guid.NewGuid(), "TST", [21], DateTime.UtcNow));
+                .Returns(new RealmKey() 
+                { 
+                    Id = Guid.NewGuid(), 
+                    KeyType = "TST", 
+                    Key = new("kid", [21]),
+                    CreatedAt = DateTime.UtcNow
+                });
             // Act
             RealmService sut = new(db, _keyService);
             var response = await sut.Create(

IdentityShroud.Core.Tests/UnitTest1.cs

@@ -2,7 +2,6 @@
 using System.Text;
 using System.Text.Json;
 using IdentityShroud.Core.DTO;
-using IdentityShroud.Core.Messages;
 using Microsoft.AspNetCore.WebUtilities;
 
 namespace IdentityShroud.Core.Tests;
@@ -67,9 +66,9 @@ public static class JwtReader
         return new JsonWebToken()
         {
             Header = JsonSerializer.Deserialize<JsonWebTokenHeader>(
-                Encoding.UTF8.GetString(WebEncoders.Base64UrlDecode(jwt, 0, firstDot))),
+                Encoding.UTF8.GetString(WebEncoders.Base64UrlDecode(jwt, 0, firstDot)))!,
             Payload = JsonSerializer.Deserialize<JsonWebTokenPayload>(
-                Encoding.UTF8.GetString(WebEncoders.Base64UrlDecode(jwt, firstDot + 1, secondDot - (firstDot + 1)))),
+                Encoding.UTF8.GetString(WebEncoders.Base64UrlDecode(jwt, firstDot + 1, secondDot - (firstDot + 1))))!,
             Signature = WebEncoders.Base64UrlDecode(jwt, secondDot + 1, jwt.Length - (secondDot + 1))
         };
     }

IdentityShroud.Core/Contracts/IClientService.cs

@@ -2,18 +2,6 @@ using IdentityShroud.Core.Model;
 
 namespace IdentityShroud.Core.Contracts;
 
-//public record CreateClientRequest(Guid RealmId, string ClientId, string? Description);
-
-public class ClientCreateRequest
-{
-    public required string ClientId { get; set; }
-    public string? Name { get; set; }
-    public string? Description { get; set; }
-    public string? SignatureAlgorithm { get; set; }
-    public bool? AllowClientCredentialsFlow { get; set; }
-}
-
-
 public interface IClientService
 {
     Task<Result<Client>> Create(
@@ -21,6 +9,6 @@ public interface IClientService
         ClientCreateRequest request, 
         CancellationToken ct = default);
 
-    Task<Client?> GetByClientId(string clientId, CancellationToken ct = default);
-    Task<Client?> FindById(int id, CancellationToken ct = default);
+    Task<Client?> GetByClientId(Guid realmId, string clientId, CancellationToken ct = default);
+    Task<Client?> FindById(Guid realmId, int id, CancellationToken ct = default);
 }

IdentityShroud.Core/Contracts/IEncryptionService.cs

@@ -2,6 +2,6 @@ namespace IdentityShroud.Core.Contracts;
 
 public interface IEncryptionService
 {
-    byte[] Encrypt(byte[] plain);
-    byte[] Decrypt(ReadOnlyMemory<byte> cipher);
+    EncryptedValue Encrypt(ReadOnlyMemory<byte> plain);
+    byte[] Decrypt(EncryptedValue input);
 }

IdentityShroud.Core/Contracts/ISecretProvider.cs

@@ -3,4 +3,10 @@ namespace IdentityShroud.Core.Contracts;
 public interface ISecretProvider
 {
     string GetSecret(string name);
+
+    /// <summary>
+    /// Should return one active key, might return inactive keys.
+    /// </summary>
+    /// <returns></returns>
+    EncryptionKey[] GetKeys(string name);
 }

IdentityShroud.Core/DTO/Client/ClientCreateRequest.cs

@@ -0,0 +1,10 @@
+namespace IdentityShroud.Core.Contracts;
+
+public class ClientCreateRequest
+{
+    public required string ClientId { get; set; }
+    public string? Name { get; set; }
+    public string? Description { get; set; }
+    public string? SignatureAlgorithm { get; set; }
+    public bool? AllowClientCredentialsFlow { get; set; }
+}

IdentityShroud.Core/Helpers/SlugHelper.cs

@@ -1,4 +1,3 @@
-using System;
 using System.Globalization;
 using System.Security.Cryptography;
 using System.Text;

IdentityShroud.Core/IdentityShroud.Core.csproj

@@ -13,6 +13,7 @@
       <PackageReference Include="jose-jwt" Version="5.2.0" />
       <PackageReference Include="LanguageExt.Core" Version="4.4.9" />
       <PackageReference Include="Microsoft.Extensions.Configuration.Binder" Version="10.0.2" />
+      <PackageReference Include="Microsoft.AspNetCore.WebUtilities" Version="10.0.2" />
       <PackageReference Include="Npgsql.EntityFrameworkCore.PostgreSQL" Version="10.0.0" />
     </ItemGroup>
     
@@ -20,10 +21,4 @@
         <Using Include="FluentResults" />
     </ItemGroup>
 
-    <ItemGroup>
-      <Reference Include="Microsoft.AspNetCore.WebUtilities">
-        <HintPath>..\..\..\.nuget\packages\microsoft.aspnetcore.webutilities\10.0.2\lib\net10.0\Microsoft.AspNetCore.WebUtilities.dll</HintPath>
-      </Reference>
-    </ItemGroup>
-
 </Project>

IdentityShroud.Core/Model/Client.cs

@@ -1,6 +1,5 @@
 using System.ComponentModel.DataAnnotations;
 using System.ComponentModel.DataAnnotations.Schema;
-using IdentityShroud.Core.Security;
 using Microsoft.EntityFrameworkCore;
 
 namespace IdentityShroud.Core.Model;

IdentityShroud.Core/Model/ClientSecret.cs

@@ -1,5 +1,6 @@
 using System.ComponentModel.DataAnnotations;
 using System.ComponentModel.DataAnnotations.Schema;
+using IdentityShroud.Core.Contracts;
 
 namespace IdentityShroud.Core.Model;
 
@@ -11,5 +12,5 @@ public class ClientSecret
     public Guid ClientId { get; set; }
     public DateTime CreatedAt { get; set; }
     public DateTime? RevokedAt { get; set; }
-    public required byte[] SecretEncrypted { get; set; }
+    public required EncryptedValue Secret { get; set; }
 }

IdentityShroud.Core/Model/Realm.cs

@@ -1,7 +1,6 @@
 using System.ComponentModel.DataAnnotations;
 using System.ComponentModel.DataAnnotations.Schema;
 using IdentityShroud.Core.Security;
-using Microsoft.EntityFrameworkCore;
 
 namespace IdentityShroud.Core.Model;
 

IdentityShroud.Core/Model/RealmKey.cs

@@ -1,15 +1,19 @@
 using System.ComponentModel.DataAnnotations.Schema;
+using IdentityShroud.Core.Contracts;
+using Microsoft.EntityFrameworkCore;
 
 namespace IdentityShroud.Core.Model;
 
 
 [Table("realm_key")]
-public record RealmKey(Guid Id, string KeyType, byte[] KeyDataEncrypted, DateTime CreatedAt)
+public record RealmKey
 {
-    public Guid Id { get; private set; } = Id;
-    public string KeyType { get; private set; } = KeyType;
-    public byte[] KeyDataEncrypted { get; private set; } = KeyDataEncrypted;
-    public DateTime CreatedAt { get; private set; } = CreatedAt;
+    public required Guid Id { get; init; }
+    public required string KeyType { get; init; }
+
+    
+    public required EncryptedValue Key { get; init; }
+    public required DateTime CreatedAt { get; init; }
     public DateTime? RevokedAt { get; set; }
 
     /// <summary>

IdentityShroud.Core/Security/AesGcmHelper.cs

@@ -1,70 +0,0 @@
-using System.Security.Cryptography;
-
-namespace IdentityShroud.Core.Security;
-
-public static class AesGcmHelper
-{
-    
-    public static byte[] EncryptAesGcm(byte[] plaintext, byte[] key)
-    {
-        int tagSize = AesGcm.TagByteSizes.MaxSize;
-        using var aes = new AesGcm(key, tagSize);
-        
-        Span<byte> nonce = stackalloc byte[AesGcm.NonceByteSizes.MaxSize];
-        RandomNumberGenerator.Fill(nonce);
-        Span<byte> ciphertext = stackalloc byte[plaintext.Length];
-        Span<byte> tag = stackalloc byte[tagSize];
-
-        aes.Encrypt(nonce, plaintext, ciphertext, tag);
-
-        // Return concatenated nonce|ciphertext|tag
-        var result = new byte[nonce.Length + ciphertext.Length + tag.Length];
-        nonce.CopyTo(result.AsSpan(0, nonce.Length));
-        ciphertext.CopyTo(result.AsSpan(nonce.Length, ciphertext.Length));
-        tag.CopyTo(result.AsSpan(nonce.Length + ciphertext.Length, tag.Length));
-        return result;
-    }
-    
-    // --------------------------------------------------------------------
-    // DecryptAesGcm
-    //   • key      – 32‑byte (256‑bit) secret key (same key used for encryption)
-    //   • payload  – byte[] containing nonce‖ciphertext‖tag
-    //   • returns  – the original plaintext bytes
-    // --------------------------------------------------------------------
-    public static byte[] DecryptAesGcm(ReadOnlyMemory<byte> payload, byte[] key)
-    {
-        if (key == null)     throw new ArgumentNullException(nameof(key));
-        if (key.Length != 32) // 256‑bit key
-            throw new ArgumentException("Key must be 256 bits (32 bytes) for AES‑256‑GCM.", nameof(key));
-
-        // ----------------------------------------------------------------
-        // 1️⃣ Extract the three components.
-        // ----------------------------------------------------------------
-        // AesGcm.NonceByteSizes.MaxSize = 12 bytes (standard GCM nonce length)
-        // AesGcm.TagByteSizes.MaxSize   = 16 bytes (128‑bit authentication tag)
-        int nonceSize = AesGcm.NonceByteSizes.MaxSize; // 12
-        int tagSize   = AesGcm.TagByteSizes.MaxSize;   // 16
-
-        if (payload.Length < nonceSize + tagSize)
-            throw new ArgumentException("Payload is too short to contain nonce, ciphertext, and tag.", nameof(payload));
-
-        ReadOnlySpan<byte> nonce = payload.Span[..nonceSize];
-        ReadOnlySpan<byte> ciphertext = payload.Span.Slice(nonceSize, payload.Length - nonceSize - tagSize);
-        ReadOnlySpan<byte> tag = payload.Span.Slice(payload.Length - tagSize, tagSize);
-
-        byte[] plaintext = new byte[ciphertext.Length];
-
-        using var aes = new AesGcm(key, tagSize);
-        try
-        {
-            aes.Decrypt(nonce, ciphertext, tag, plaintext);
-        }
-        catch (CryptographicException ex)
-        {
-            // Tag verification failed → tampering or wrong key/nonce.
-            throw new InvalidOperationException("Decryption failed – authentication tag mismatch.", ex);
-        }
-
-        return plaintext;
-    }
-}

IdentityShroud.Core/Security/ConfigurationSecretProvider.cs

@@ -14,4 +14,9 @@ public class ConfigurationSecretProvider(IConfiguration configuration) : ISecret
     {
         return secrets.GetValue<string>(name) ?? "";
     }
+
+    public EncryptionKey[] GetKeys(string name)
+    {
+        return secrets.GetSection(name).Get<EncryptionKey[]>() ?? [];
+    }
 }

IdentityShroud.Core/Security/EncryptedValue.cs

@@ -0,0 +1,6 @@
+using Microsoft.EntityFrameworkCore;
+
+namespace IdentityShroud.Core.Contracts;
+
+[Owned]
+public record EncryptedValue(string KeyId, byte[] Value);

IdentityShroud.Core/Security/EncryptionKey.cs

@@ -0,0 +1,4 @@
+namespace IdentityShroud.Core.Contracts;
+
+// Contains an encryption key and associated relevant data
+public record EncryptionKey(string Id, bool Active, string Algorithm, byte[] Key);

IdentityShroud.Core/Security/JsonWebAlgorithm.cs

@@ -1,5 +1,3 @@
-using System.Security.Cryptography;
-
 namespace IdentityShroud.Core.Security;
 
 public static class JsonWebAlgorithm

IdentityShroud.Core/Security/Keys/IKeyProvider.cs

@@ -1,5 +1,4 @@
 using IdentityShroud.Core.Messages;
-using IdentityShroud.Core.Model;
 
 namespace IdentityShroud.Core.Security.Keys;
 

IdentityShroud.Core/Security/Keys/Rsa/RsaProvider.cs

@@ -1,8 +1,6 @@
 using System.Buffers.Text;
 using System.Security.Cryptography;
-using IdentityShroud.Core.Contracts;
 using IdentityShroud.Core.Messages;
-using IdentityShroud.Core.Model;
 
 namespace IdentityShroud.Core.Security.Keys.Rsa;
 

IdentityShroud.Core/Security/RsaHelper.cs

@@ -1,16 +0,0 @@
-using System.Security.Cryptography;
-
-namespace IdentityShroud.Core.Security;
-
-public static class RsaHelper
-{
-    /// <summary>
-    /// Load RSA private key from PKCS#8 format
-    /// </summary>
-    public static RSA LoadFromPkcs8(byte[] pkcs8Key)
-    {
-        var rsa = RSA.Create();
-        rsa.ImportPkcs8PrivateKey(pkcs8Key, out _);
-        return rsa;
-    }
-}

IdentityShroud.Core/Services/ClientService.cs

@@ -34,14 +34,20 @@ public class ClientService(
         return client;
     }
 
-    public async Task<Client?> GetByClientId(string clientId, CancellationToken ct = default)
+    public async Task<Client?> GetByClientId(
+        Guid realmId,
+        string clientId, 
+        CancellationToken ct = default)
     {
-        return await db.Clients.FirstOrDefaultAsync(c => c.ClientId == clientId, ct);
+        return await db.Clients.FirstOrDefaultAsync(c => c.ClientId == clientId && c.RealmId == realmId, ct);
     }
 
-    public async Task<Client?> FindById(int id, CancellationToken ct = default)
+    public async Task<Client?> FindById(
+        Guid realmId,
+        int id, 
+        CancellationToken ct = default)
     {
-        return await db.Clients.FirstOrDefaultAsync(c => c.Id == id, ct);
+        return await db.Clients.FirstOrDefaultAsync(c => c.Id == id && c.RealmId == realmId, ct);
     }
 
     private ClientSecret CreateSecret()
@@ -51,7 +57,7 @@ public class ClientService(
         return new ClientSecret()
         {
             CreatedAt = clock.UtcNow(),
-            SecretEncrypted = cryptor.Encrypt(secret),
+            Secret = cryptor.Encrypt(secret),
         };
 
     }

IdentityShroud.Core/Services/EncryptionService.cs

@@ -1,5 +1,5 @@
+using System.Security.Cryptography;
 using IdentityShroud.Core.Contracts;
-using IdentityShroud.Core.Security;
 
 namespace IdentityShroud.Core.Services;
 
@@ -8,20 +8,85 @@ namespace IdentityShroud.Core.Services;
 /// </summary>
 public class EncryptionService : IEncryptionService
 {
-    private readonly byte[] encryptionKey;
+    private record struct AlgVersion(int NonceSize, int TagSize);
+
+    private AlgVersion[] _versions = 
+    [
+        new(0, 0), // version 0 does not realy exist
+        new (12, 16), // version 1
+    ];
+    
+    // Note this array is expected to have one item in it most of the during key rotation it will have two
+    // until it is ensured the old key can safely be removed. More then two will work but is not really expected.
+    private readonly EncryptionKey[] _encryptionKeys;
+
+    private EncryptionKey ActiveKey => _encryptionKeys.Single(k => k.Active);
+    private EncryptionKey GetKey(string keyId) => _encryptionKeys.Single(k => k.Id == keyId);
 
     public EncryptionService(ISecretProvider secretProvider)
     {
-        encryptionKey = Convert.FromBase64String(secretProvider.GetSecret("Master"));
+        _encryptionKeys = secretProvider.GetKeys("master");
+        // if (_encryptionKey.Length != 32) // 256‑bit key
+        //     throw new Exception("Key must be 256 bits (32 bytes) for AES‑256‑GCM.");
     }
 
-    public byte[] Encrypt(byte[] plain)
+    public EncryptedValue Encrypt(ReadOnlyMemory<byte> plaintext)
     {
-        return AesGcmHelper.EncryptAesGcm(plain, encryptionKey);
+        const int versionNumber = 1; 
+        AlgVersion versionParams = _versions[versionNumber];
+
+        int resultSize = 1 + versionParams.NonceSize + versionParams.TagSize + plaintext.Length;
+        // allocate buffer for complete response 
+        var result = new byte[resultSize];
+        
+        result[0] = (byte)versionNumber;
+
+        // make the spans that point to the parts of the result where their data is located
+        var nonce = result.AsSpan(1, versionParams.NonceSize); 
+        var tag = result.AsSpan(1 + versionParams.NonceSize, versionParams.TagSize);
+        var cipher = result.AsSpan(1 + versionParams.NonceSize + versionParams.TagSize);
+
+        // use the spans to place the data directly in its place
+        RandomNumberGenerator.Fill(nonce);
+        var encryptionKey = ActiveKey;
+        using var aes = new AesGcm(encryptionKey.Key, versionParams.TagSize);
+        aes.Encrypt(nonce, plaintext.Span, cipher, tag);
+
+        return new (encryptionKey.Id, result);
     }
 
-    public byte[] Decrypt(ReadOnlyMemory<byte> cipher)
+    public byte[] Decrypt(EncryptedValue input)
     {
-        return AesGcmHelper.DecryptAesGcm(cipher, encryptionKey);
+        var encryptionKey = GetKey(input.KeyId);
+        
+        var payload = input.Value.AsSpan();
+        int versionNumber = (int)payload[0];
+        if (versionNumber != 1)
+            throw new ArgumentException("Invalid payload");
+        
+        AlgVersion versionParams = _versions[versionNumber];
+        
+        
+        if (payload.Length < 1 + versionParams.NonceSize + versionParams.TagSize)
+            throw new ArgumentException("Payload is too short to contain nonce, ciphertext, and tag.", nameof(payload));
+
+        ReadOnlySpan<byte> nonce = payload.Slice(1, versionParams.NonceSize);
+        ReadOnlySpan<byte> tag = payload.Slice(1 + versionParams.NonceSize, versionParams.TagSize);
+        ReadOnlySpan<byte> cipher = payload.Slice(1 + versionParams.NonceSize + versionParams.TagSize);
+
+        byte[] plaintext = new byte[cipher.Length];
+
+        using var aes = new AesGcm(encryptionKey.Key, versionParams.TagSize);
+        try
+        {
+            aes.Decrypt(nonce, cipher, tag, plaintext);
+        }
+        catch (CryptographicException ex)
+        {
+            // Tag verification failed → tampering or wrong key/nonce.
+            throw new InvalidOperationException("Decryption failed – authentication tag mismatch.", ex);
+        }
+
+        return plaintext;
     }
 }

IdentityShroud.Core/Services/KeyService.cs

@@ -1,4 +1,3 @@
-using System.Security.Cryptography;
 using IdentityShroud.Core.Contracts;
 using IdentityShroud.Core.Messages;
 using IdentityShroud.Core.Model;
@@ -30,23 +29,18 @@ public class KeyService(
         
         IKeyProvider provider = keyProviderFactory.CreateProvider(realmKey.KeyType);
         provider.SetJwkParameters(
-            cryptor.Decrypt(realmKey.KeyDataEncrypted),
+            cryptor.Decrypt(realmKey.Key),
             jwk);
 
         return jwk;
     }
 
     private RealmKey CreateKey(string keyType, byte[] plainKey) =>
-        new RealmKey(
-            Guid.NewGuid(),
-            keyType,
-            cryptor.Encrypt(plainKey),
-            clock.UtcNow());
-
-    // public byte[] GetPrivateKey(IEncryptionService encryptionService)
-    // {
-    //     if (_privateKeyDecrypted.Length == 0 && PrivateKeyEncrypted.Length > 0)
-    //         _privateKeyDecrypted = encryptionService.Decrypt(PrivateKeyEncrypted);
-    //     return _privateKeyDecrypted;
-    // }
+        new RealmKey()
+            {
+                Id = Guid.NewGuid(),
+                KeyType = keyType,
+                Key = cryptor.Encrypt(plainKey),
+                CreatedAt = clock.UtcNow(),
+            };
 }

IdentityShroud.Core/Services/RealmService.cs

@@ -1,4 +1,3 @@
-using System.Security.Cryptography;
 using IdentityShroud.Core.Contracts;
 using IdentityShroud.Core.Helpers;
 using IdentityShroud.Core.Messages.Realm;

IdentityShroud.TestUtils/Asserts/JsonObjectAssert.cs

@@ -1,6 +1,5 @@
 using System.Text.Json.Nodes;
 using System.Text.RegularExpressions;
-using Xunit;
 
 namespace IdentityShroud.TestUtils.Asserts;
 

IdentityShroud.TestUtils/Asserts/ResultAssert.cs

@@ -1,5 +1,4 @@
 using FluentResults;
-using Xunit;
 
 namespace IdentityShroud.Core.Tests;
 

IdentityShroud.TestUtils/IdentityShroud.TestUtils.csproj

@@ -10,6 +10,7 @@
     <ItemGroup>
       <PackageReference Include="FluentResults" Version="4.0.0" />
       <PackageReference Include="xunit.v3.assert" Version="3.2.2" />
+      <PackageReference Include="NSubstitute" Version="5.3.0" />
     </ItemGroup>
 
     <ItemGroup>
@@ -21,10 +22,4 @@
         <Using Include="NSubstitute"/>
     </ItemGroup>
 
-    <ItemGroup>
-      <Reference Include="NSubstitute">
-        <HintPath>..\..\..\.nuget\packages\nsubstitute\5.3.0\lib\net6.0\NSubstitute.dll</HintPath>
-      </Reference>
-    </ItemGroup>
-
 </Project>

IdentityShroud.TestUtils/Substitutes/EncryptionServiceSubstitute.cs

@@ -8,11 +8,11 @@ public static class EncryptionServiceSubstitute
     {
         var encryptionService = Substitute.For<IEncryptionService>();
         encryptionService
-            .Encrypt(Arg.Any<byte[]>())
-            .Returns(x => x.ArgAt<byte[]>(0));
+            .Encrypt(Arg.Any<ReadOnlyMemory<byte>>())
+            .Returns(x => new EncryptedValue("kid", x.ArgAt<ReadOnlyMemory<byte>>(0).ToArray()));
         encryptionService
-            .Decrypt(Arg.Any<ReadOnlyMemory<byte>>())
-            .Returns(x => x.ArgAt<ReadOnlyMemory<byte>>(0).ToArray());
+            .Decrypt(Arg.Any<EncryptedValue>())
+            .Returns(x => x.ArgAt<EncryptedValue>(0).Value);
         return encryptionService;
     }
 }

IdentityShroud.sln.DotSettings.user

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+	
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 	<s:String x:Key="/Default/Environment/Hierarchy/Build/BuildTool/CustomBuildToolPath/@EntryValue">/home/eelke/.dotnet/sdk/10.0.102/MSBuild.dll</s:String>
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-&lt;/SessionState&gt;</s:String>
+	
+	
+	
 	
 	
 	

README.md

@@ -0,0 +1,15 @@
+# IdentityShroud
+
+IdentityShroud is a .NET project for identity management and protection.
+
+## Build and Test
+
+```bash
+dotnet restore
+dotnet build
+dotnet test
+```
+
+## Coverage
+
+Coverage reports are generated automatically in CI and displayed in pull request comments.