diff --git a/lib/diaspora_federation/entities/participation.rb b/lib/diaspora_federation/entities/participation.rb
index b6a8852..73cf2d3 100644
--- a/lib/diaspora_federation/entities/participation.rb
+++ b/lib/diaspora_federation/entities/participation.rb
@@ -15,6 +15,22 @@ module DiasporaFederation
       #   currently only "Post" is supported.
       #   @return [String] parent type
       property :parent_type, xml_name: :target_type
+
+      # It is only valid to receive a {Participation} from the author itself.
+      # @deprecated remove after {Participation} doesn't include {Relayable} anymore
+      def sender_valid?(sender)
+        sender == author
+      end
+
+      # Default implementation, don't verify signatures for a {Participation}.
+      # @see Entity.populate_entity
+      # @deprecated remove after {Participation} doesn't include {Relayable} anymore
+      # @param [Nokogiri::XML::Element] root_node xml nodes
+      # @return [Entity] instance
+      def self.populate_entity(root_node)
+        new(entity_data(root_node).merge(parent: nil))
+      end
+      private_class_method :populate_entity
     end
   end
 end
diff --git a/lib/diaspora_federation/validators/participation_validator.rb b/lib/diaspora_federation/validators/participation_validator.rb
index 7d8baff..5fc5c87 100644
--- a/lib/diaspora_federation/validators/participation_validator.rb
+++ b/lib/diaspora_federation/validators/participation_validator.rb
@@ -4,8 +4,9 @@ module DiasporaFederation
     class ParticipationValidator < Validation::Validator
       include Validation
 
-      include RelayableValidator
-
+      rule :author, %i(not_empty diaspora_id)
+      rule :guid, :guid
+      rule :parent_guid, :guid
       rule :parent_type, [:not_empty, regular_expression: {regex: /\APost\z/}]
     end
   end
diff --git a/spec/lib/diaspora_federation/entities/participation_spec.rb b/spec/lib/diaspora_federation/entities/participation_spec.rb
index 2b348d8..fd091ae 100644
--- a/spec/lib/diaspora_federation/entities/participation_spec.rb
+++ b/spec/lib/diaspora_federation/entities/participation_spec.rb
@@ -28,8 +28,31 @@ XML
 
     it_behaves_like "an Entity subclass"
 
-    it_behaves_like "an XML Entity"
+    it_behaves_like "an XML Entity", [:parent]
 
     it_behaves_like "a relayable Entity"
+
+    describe "#sender_valid?" do
+      let(:entity) { Entities::Participation.new(data) }
+
+      it "allows the author" do
+        expect(entity.sender_valid?(alice.diaspora_id)).to be_truthy
+      end
+
+      it "does not allow the parent author" do
+        expect(entity.sender_valid?(bob.diaspora_id)).to be_falsey
+      end
+    end
+
+    context "relayable signature verification" do
+      it "does not verify the signature" do
+        data.merge!(author_signature: "aa", parent_author_signature: "bb")
+        xml = Entities::Participation.new(data).to_xml
+
+        expect {
+          Entities::Participation.from_xml(xml)
+        }.not_to raise_error
+      end
+    end
   end
 end
diff --git a/spec/lib/diaspora_federation/validators/participation_validator_spec.rb b/spec/lib/diaspora_federation/validators/participation_validator_spec.rb
index 91efd44..29606fa 100644
--- a/spec/lib/diaspora_federation/validators/participation_validator_spec.rb
+++ b/spec/lib/diaspora_federation/validators/participation_validator_spec.rb
@@ -4,7 +4,22 @@ module DiasporaFederation
 
     it_behaves_like "a common validator"
 
-    it_behaves_like "a relayable validator"
+    it_behaves_like "a diaspora id validator" do
+      let(:property) { :author }
+      let(:mandatory) { true }
+    end
+
+    describe "#guid" do
+      it_behaves_like "a guid validator" do
+        let(:property) { :guid }
+      end
+    end
+
+    describe "#parent_guid" do
+      it_behaves_like "a guid validator" do
+        let(:property) { :parent_guid }
+      end
+    end
 
     describe "#parent_type" do
       it_behaves_like "a property with a value validation/restriction" do