diff --git a/lib/diaspora_federation/entities.rb b/lib/diaspora_federation/entities.rb
index 6760c56..11c0326 100644
--- a/lib/diaspora_federation/entities.rb
+++ b/lib/diaspora_federation/entities.rb
@@ -12,6 +12,7 @@ require "diaspora_federation/entities/related_entity"
 
 # abstract types
 require "diaspora_federation/entities/post"
+require "diaspora_federation/entities/signable"
 require "diaspora_federation/entities/relayable"
 
 # types
diff --git a/lib/diaspora_federation/entities/relayable.rb b/lib/diaspora_federation/entities/relayable.rb
index 4ed432f..b293e7c 100644
--- a/lib/diaspora_federation/entities/relayable.rb
+++ b/lib/diaspora_federation/entities/relayable.rb
@@ -5,10 +5,7 @@ module DiasporaFederation
     # has a parent, identified by guid. Relayables are also signed and signing/verification
     # logic is embedded into Salmon XML processing code.
     module Relayable
-      include Logging
-
-      # Digest instance used for signing
-      DIGEST = OpenSSL::Digest::SHA256.new
+      include Signable
 
       # Order from the parsed xml for signature
       # @return [Array] order from xml
@@ -107,24 +104,6 @@ module DiasporaFederation
 
       private
 
-      # Check that signature is a correct signature
-      #
-      # @param [String] author The author of the signature
-      # @param [String] signature_key The signature to be verified
-      # @return [Boolean] signature valid
-      def verify_signature(author, signature_key)
-        pubkey = DiasporaFederation.callbacks.trigger(:fetch_public_key, author)
-        raise PublicKeyNotFound, "signature=#{signature_key} person=#{author} obj=#{self}" if pubkey.nil?
-
-        signature = public_send(signature_key)
-        raise SignatureVerificationFailed, "no #{signature_key} for #{self}" if signature.nil?
-
-        valid = pubkey.verify(DIGEST, Base64.decode64(signature), signature_data)
-        raise SignatureVerificationFailed, "wrong #{signature_key} for #{self}" unless valid
-
-        logger.info "event=verify_signature signature=#{signature_key} status=valid obj=#{self}"
-      end
-
       # Sign with author key
       # @raise [AuthorPrivateKeyNotFound] if the author private key is not found
       # @return [String] A Base64 encoded signature of #signature_data with key
@@ -147,14 +126,6 @@ module DiasporaFederation
         end
       end
 
-      # Sign the data with the key
-      #
-      # @param [OpenSSL::PKey::RSA] privkey An RSA key
-      # @return [String] A Base64 encoded signature of #signature_data with key
-      def sign_with_key(privkey)
-        Base64.strict_encode64(privkey.sign(DIGEST, signature_data))
-      end
-
       # Update the signatures with the keys of the author and the parent
       # if the signatures are not there yet and if the keys are available.
       #
@@ -245,14 +216,6 @@ module DiasporaFederation
       # Raised, if creating the author_signature fails, because the private key was not found
       class AuthorPrivateKeyNotFound < RuntimeError
       end
-
-      # Raised, if verify_signatures fails to verify signatures (no public key found)
-      class PublicKeyNotFound < RuntimeError
-      end
-
-      # Raised, if verify_signatures fails to verify signatures (signatures are wrong)
-      class SignatureVerificationFailed < RuntimeError
-      end
     end
   end
 end
diff --git a/lib/diaspora_federation/entities/signable.rb b/lib/diaspora_federation/entities/signable.rb
new file mode 100644
index 0000000..e020452
--- /dev/null
+++ b/lib/diaspora_federation/entities/signable.rb
@@ -0,0 +1,53 @@
+module DiasporaFederation
+  module Entities
+    # Signable is a module that encapsulates basic signature generation/verification flow for entities.
+    module Signable
+      include Logging
+
+      # Digest instance used for signing
+      DIGEST = OpenSSL::Digest::SHA256.new
+
+      # Sign the data with the key
+      #
+      # @param [OpenSSL::PKey::RSA] privkey An RSA key
+      # @return [String] A Base64 encoded signature of #signature_data with key
+      def sign_with_key(privkey)
+        Base64.strict_encode64(privkey.sign(DIGEST, signature_data))
+      end
+
+      # Check that signature is a correct signature
+      #
+      # @param [String] author The author of the signature
+      # @param [String] signature_key The signature to be verified
+      # @return [Boolean] signature valid
+      def verify_signature(author, signature_key)
+        pubkey = DiasporaFederation.callbacks.trigger(:fetch_public_key, author)
+        raise PublicKeyNotFound, "signature=#{signature_key} person=#{author} obj=#{self}" if pubkey.nil?
+
+        signature = public_send(signature_key)
+        raise SignatureVerificationFailed, "no #{signature_key} for #{self}" if signature.nil?
+
+        valid = pubkey.verify(DIGEST, Base64.decode64(signature), signature_data)
+        raise SignatureVerificationFailed, "wrong #{signature_key} for #{self}" unless valid
+
+        logger.info "event=verify_signature signature=#{signature_key} status=valid obj=#{self}"
+      end
+
+      # This method defines what data is used for a signature creation/verification
+      #
+      # @abstract
+      # @return [String] a string to sign
+      def signature_data
+        raise NotImplementedError.new("you must override this method to define signature base string")
+      end
+
+      # Raised, if verify_signatures fails to verify signatures (no public key found)
+      class PublicKeyNotFound < RuntimeError
+      end
+
+      # Raised, if verify_signatures fails to verify signatures (signatures are wrong)
+      class SignatureVerificationFailed < RuntimeError
+      end
+    end
+  end
+end
diff --git a/spec/lib/diaspora_federation/entities/relayable_spec.rb b/spec/lib/diaspora_federation/entities/relayable_spec.rb
index 9161fc7..004d25e 100644
--- a/spec/lib/diaspora_federation/entities/relayable_spec.rb
+++ b/spec/lib/diaspora_federation/entities/relayable_spec.rb
@@ -15,14 +15,6 @@ module DiasporaFederation
 
     let(:legacy_signature_data) { "#{guid};#{author};#{property};#{parent_guid}" }
 
-    def sign_with_key(privkey, signature_data)
-      Base64.strict_encode64(privkey.sign(OpenSSL::Digest::SHA256.new, signature_data))
-    end
-
-    def verify_signature(pubkey, signature, signed_string)
-      pubkey.verify(OpenSSL::Digest::SHA256.new, Base64.decode64(signature), signed_string)
-    end
-
     describe "#initialize" do
       it "filters signatures from order" do
         xml_order = [:author, :guid, :parent_guid, :property, "new_property", :author_signature]
diff --git a/spec/lib/diaspora_federation/entities/signable_spec.rb b/spec/lib/diaspora_federation/entities/signable_spec.rb
new file mode 100644
index 0000000..bcb31c3
--- /dev/null
+++ b/spec/lib/diaspora_federation/entities/signable_spec.rb
@@ -0,0 +1,77 @@
+module DiasporaFederation
+  describe Entities::Signable do
+    TEST_STRING_VALUE = "abc123".freeze
+    let(:private_key) { OpenSSL::PKey::RSA.generate(1024) }
+    let(:test_string) { TEST_STRING_VALUE }
+    let(:test_signature) { sign_with_key(private_key, test_string) }
+
+    class TestSignableEntity < Entity
+      include Entities::Signable
+
+      property :my_signature, :string, default: nil
+
+      def signature_data
+        TEST_STRING_VALUE
+      end
+    end
+
+    describe "#signature_data" do
+      it "raises NotImplementedError when not overridden" do
+        class TestEntity < Entity
+          include Entities::Signable
+        end
+
+        expect {
+          TestEntity.new({}).signature_data
+        }.to raise_error(NotImplementedError)
+      end
+    end
+
+    describe "#sign_with_key" do
+      it "produces a correct signature" do
+        signature = TestSignableEntity.new({}).sign_with_key(private_key)
+        expect(verify_signature(private_key.public_key, signature, test_string)).to be_truthy
+      end
+    end
+
+    describe "#verify_signature" do
+      it "doesn't raise if signature is correct" do
+        expect_callback(:fetch_public_key, "id@example.tld").and_return(private_key.public_key)
+
+        expect {
+          TestSignableEntity
+            .new(my_signature: test_signature)
+            .verify_signature("id@example.tld", :my_signature)
+        }.not_to raise_error
+      end
+
+      it "raises PublicKeyNotFound when key isn't provided" do
+        expect_callback(:fetch_public_key, "id@example.tld").and_return(nil)
+
+        expect {
+          TestSignableEntity
+            .new(my_signature: test_signature)
+            .verify_signature("id@example.tld", :my_signature)
+        }.to raise_error(Entities::Signable::PublicKeyNotFound)
+      end
+
+      it "raises SignatureVerificationFailed when signature isn't provided" do
+        expect_callback(:fetch_public_key, "id@example.tld").and_return(private_key.public_key)
+
+        expect {
+          TestSignableEntity.new({}).verify_signature("id@example.tld", :my_signature)
+        }.to raise_error(Entities::Signable::SignatureVerificationFailed)
+      end
+
+      it "raises SignatureVerificationFailed when signature is wrong" do
+        expect_callback(:fetch_public_key, "id@example.tld").and_return(private_key.public_key)
+
+        expect {
+          TestSignableEntity
+            .new(my_signature: "faked signature")
+            .verify_signature("id@example.tld", :my_signature)
+        }.to raise_error(Entities::Signable::SignatureVerificationFailed)
+      end
+    end
+  end
+end
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 9f07f48..c5f7454 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -45,6 +45,14 @@ def add_signatures(hash, klass=described_class)
   hash[:parent_author_signature] = properties[:parent_author_signature]
 end
 
+def sign_with_key(privkey, signature_data)
+  Base64.strict_encode64(privkey.sign(OpenSSL::Digest::SHA256.new, signature_data))
+end
+
+def verify_signature(pubkey, signature, signed_string)
+  pubkey.verify(OpenSSL::Digest::SHA256.new, Base64.decode64(signature), signed_string)
+end
+
 # Requires supporting files with custom matchers and macros, etc,
 # in ./support/ and its subdirectories.
 fixture_builder_file = "#{File.dirname(__FILE__)}/support/fixture_builder.rb"