diff --git a/LibMatrix.Federation/Extensions/SignedObjectExtensions.cs b/LibMatrix.Federation/Extensions/SignedObjectExtensions.cs
new file mode 100644
index 0000000..eb1376e
--- /dev/null
+++ b/LibMatrix.Federation/Extensions/SignedObjectExtensions.cs
@@ -0,0 +1,37 @@
+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 SignedObjectExtensions {
+ public static SignedObject<T> Sign<T>(this SignedObject<T> content, string serverName, string keyName, Ed25519PrivateKeyParameters key) {
+ var signResult = content.Content.Sign(serverName, keyName, key);
+ var signedObject = new SignedObject<T> {
+ Signatures = content.Signatures,
+ Content = signResult.Content
+ };
+
+ if (!signedObject.Signatures.ContainsKey(serverName))
+ signedObject.Signatures[serverName] = new Dictionary<string, string>();
+
+ signedObject.Signatures[serverName][keyName] = signResult.Signatures[serverName][keyName];
+ return signedObject;
+ }
+
+ public static bool ValidateSignature<T>(this SignedObject<T> content, string serverName, string keyName, Ed25519PublicKeyParameters key) {
+ if (!content.Signatures.TryGetValue(serverName, out var serverSignatures))
+ return false;
+
+ if (!serverSignatures.TryGetValue(keyName, out var signatureBase64))
+ return false;
+
+ var signature = UnpaddedBase64.Decode(signatureBase64);
+ if (signature.Length != Ed25519.SignatureSize)
+ return false;
+
+ var contentBytes = CanonicalJsonSerializer.SerializeToUtf8Bytes(content.Content);
+ return Ed25519.Verify(signature, 0, key.GetEncoded(), 0, contentBytes, 0, contentBytes.Length);
+ }
+}
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