diff --git a/LibMatrix.Federation/Extensions/ObjectExtensions.cs b/LibMatrix.Federation/Extensions/ObjectExtensions.cs
new file mode 100644
index 0000000..d20385d
--- /dev/null
+++ b/LibMatrix.Federation/Extensions/ObjectExtensions.cs
@@ -0,0 +1,31 @@
+using System.Text.Json;
+using System.Text.Json.Nodes;
+using LibMatrix.Abstractions;
+using LibMatrix.Extensions;
+using LibMatrix.FederationTest.Utilities;
+using LibMatrix.Responses.Federation;
+using Org.BouncyCastle.Crypto.Parameters;
+using Org.BouncyCastle.Math.EC.Rfc8032;
+
+namespace LibMatrix.Federation.Extensions;
+public static class ObjectExtensions {
+ public static SignedObject<T> Sign<T>(this T content, string serverName, string keyName, Ed25519PrivateKeyParameters key) {
+ SignedObject<T> signedObject = new() {
+ Signatures = [],
+ Content = JsonSerializer.Deserialize<JsonObject>(JsonSerializer.Serialize(content)) ?? new JsonObject(),
+ };
+
+ var contentBytes = CanonicalJsonSerializer.SerializeToUtf8Bytes(signedObject.Content);
+ var signature = new byte[Ed25519.SignatureSize];
+ key.Sign(Ed25519.Algorithm.Ed25519, null, contentBytes, 0, contentBytes.Length, signature, 0);
+
+ if (!signedObject.Signatures.ContainsKey(serverName))
+ signedObject.Signatures[serverName] = new Dictionary<string, string>();
+
+ signedObject.Signatures[serverName][keyName] = UnpaddedBase64.Encode(signature);
+ return signedObject;
+ }
+
+ public static SignedObject<T> Sign<T>(this T content, VersionedHomeserverPrivateKey privateKey)
+ => Sign(content, privateKey.ServerName, privateKey.KeyId, privateKey.GetPrivateEd25519Key());
+}
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