feat(core): define primary models and services for encryption

src/FiscalOS.Core/Security/EncryptedDataKey.cs

@@ -0,0 +1,21 @@
+namespace FiscalOS.Core.Security;
+
+public sealed record EncryptedDataKey
+{
+  public string KeyIdUsed { get; init; }
+  public string EncryptedKey { get; init; }
+
+  private EncryptedDataKey(string keyIdUsed, string encryptedKey)
+  {
+    KeyIdUsed = keyIdUsed;
+    EncryptedKey = encryptedKey;
+  }
+
+  public static EncryptedDataKey From(string keyIdUsed, string encryptedKey)
+  {
+    ArgumentNullException.ThrowIfNull(keyIdUsed);
+    ArgumentNullException.ThrowIfNull(encryptedKey);
+
+    return new(keyIdUsed, encryptedKey);
+  }
+}

src/FiscalOS.Core/Security/IEncryptor.cs

@@ -0,0 +1,11 @@
+namespace FiscalOS.Core.Security;
+
+public interface IEncryptor
+{
+  string GenerateKey();
+  Task<EncryptedDataKey> GenerateEncryptedKeyAsync(CancellationToken ct);
+  Task<string> EncryptAsync(string plainText, CancellationToken ct);
+  Task<string> EncryptAsyncFor(User user, string plainText, CancellationToken ct);
+  Task<string> DecryptAsync(string cipherText, CancellationToken ct);
+  Task<string> DecryptAsyncFor(User user, string plainText, CancellationToken ct);
+}

src/FiscalOS.Core/Security/IKeyRing.cs

@@ -0,0 +1,8 @@
+namespace FiscalOS.Core.Security;
+
+public interface IKeyRing
+{
+  KeyRingEntry GetKey(string keyId);
+  KeyRingEntry GetPrimaryKey();
+  Task<KeyRingEntry> SaveKeyAsync(string key);
+}

src/FiscalOS.Core/Security/KeyRingEntry.cs

@@ -0,0 +1,21 @@
+namespace FiscalOS.Core.Security;
+
+public sealed record KeyRingEntry
+{
+  public string KeyId { get; init; }
+  public string Key { get; init; }
+
+  private KeyRingEntry(string keyId, string key)
+  {
+    KeyId = keyId;
+    Key = key;
+  }
+
+  public static KeyRingEntry From(string keyId, string key)
+  {
+    ArgumentNullException.ThrowIfNull(keyId);
+    ArgumentNullException.ThrowIfNull(key);
+
+    return new(keyId, key);
+  }
+}

src/FiscalOS.Core/Usings.cs

@@ -1,3 +1,3 @@
 global using FiscalOS.Core.Data;
-
 global using FiscalOS.Core.Identity;
+global using FiscalOS.Core.Security;