diff --git a/lib/saml_idp/assertion_builder.rb b/lib/saml_idp/assertion_builder.rb
index 39e43e08..00dc7a99 100644
--- a/lib/saml_idp/assertion_builder.rb
+++ b/lib/saml_idp/assertion_builder.rb
@@ -16,10 +16,12 @@ class AssertionBuilder
     attr_accessor :expiry
     attr_accessor :encryption_opts
     attr_accessor :session_expiry
+    attr_accessor :x509_certificate
+    attr_accessor :secret_key
 
     delegate :config, to: :SamlIdp
 
-    def initialize(reference_id, issuer_uri, principal, audience_uri, saml_request_id, saml_acs_url, raw_algorithm, authn_context_classref, expiry=60*60, encryption_opts=nil, session_expiry=nil)
+    def initialize(reference_id, issuer_uri, principal, audience_uri, saml_request_id, saml_acs_url, raw_algorithm, authn_context_classref, expiry=60*60, encryption_opts=nil, session_expiry=nil, cert=nil, sec_key=nil)
       self.reference_id = reference_id
       self.issuer_uri = issuer_uri
       self.principal = principal
@@ -31,6 +33,8 @@ def initialize(reference_id, issuer_uri, principal, audience_uri, saml_request_i
       self.expiry = expiry
       self.encryption_opts = encryption_opts
       self.session_expiry = session_expiry.nil? ? config.session_expiry : session_expiry
+      self.x509_certificate = cert
+      self.secret_key = sec_key
     end
 
     def fresh
@@ -40,7 +44,7 @@ def fresh
         IssueInstant: now_iso,
         Version: "2.0" do |assertion|
           assertion.Issuer issuer_uri
-          sign assertion
+          sign(assertion, self.x509_certificate, self.secret_key)
           assertion.Subject do |subject|
             subject.NameID name_id, Format: name_id_format[:name]
             subject.SubjectConfirmation Method: Saml::XML::Namespaces::Methods::BEARER do |confirmation|
diff --git a/lib/saml_idp/controller.rb b/lib/saml_idp/controller.rb
index 0c8381ad..6ce24a1c 100644
--- a/lib/saml_idp/controller.rb
+++ b/lib/saml_idp/controller.rb
@@ -64,6 +64,8 @@ def encode_authn_response(principal, opts = {})
       expiry = opts[:expiry] || 60*60
       session_expiry = opts[:session_expiry]
       encryption_opts = opts[:encryption] || nil
+      certificate = opts[:certificate]
+      secret_key = opts[:secret_key]
 
       SamlResponse.new(
         reference_id,
@@ -77,7 +79,9 @@ def encode_authn_response(principal, opts = {})
         my_authn_context_classref,
         expiry,
         encryption_opts,
-        session_expiry
+        session_expiry,
+        certificate,
+        secret_key
       ).build
     end
 
diff --git a/lib/saml_idp/saml_response.rb b/lib/saml_idp/saml_response.rb
index ceac0ac1..cea8657f 100644
--- a/lib/saml_idp/saml_response.rb
+++ b/lib/saml_idp/saml_response.rb
@@ -29,7 +29,9 @@ def initialize(reference_id,
           authn_context_classref,
           expiry=60*60,
           encryption_opts=nil,
-          session_expiry=0
+          session_expiry=0,
+          cert=nil,
+          sec_key=nil
           )
       self.reference_id = reference_id
       self.response_id = response_id
@@ -39,8 +41,8 @@ def initialize(reference_id,
       self.saml_request_id = saml_request_id
       self.saml_acs_url = saml_acs_url
       self.algorithm = algorithm
-      self.secret_key = secret_key
-      self.x509_certificate = x509_certificate
+      self.secret_key = sec_key || secret_key
+      self.x509_certificate = cert || x509_certificate
       self.authn_context_classref = authn_context_classref
       self.expiry = expiry
       self.encryption_opts = encryption_opts
@@ -76,7 +78,9 @@ def assertion_builder
         authn_context_classref,
         expiry,
         encryption_opts,
-        session_expiry
+        session_expiry,
+        x509_certificate,
+        secret_key
     end
     private :assertion_builder
   end
diff --git a/lib/saml_idp/signable.rb b/lib/saml_idp/signable.rb
index b6259486..0dc039f3 100644
--- a/lib/saml_idp/signable.rb
+++ b/lib/saml_idp/signable.rb
@@ -20,8 +20,8 @@ def signed
       end
     end
 
-    def sign(el)
-      el << signature if sign?
+    def sign(el, cert=nil, sec_key=nil)
+      el << signature(cert, sec_key) if sign?
     end
 
     def generated_reference_id
@@ -64,13 +64,13 @@ def sign?
     end
     private :sign?
 
-    def signature
-      SignatureBuilder.new(signed_info_builder).raw
+    def signature(cert=nil, sec_key=nil)
+      SignatureBuilder.new(signed_info_builder(sec_key), cert).raw
     end
     private :signature
 
-    def signed_info_builder
-      SignedInfoBuilder.new(get_reference_id, get_digest, get_algorithm)
+    def signed_info_builder(sec_key=nil)
+      SignedInfoBuilder.new(get_reference_id, get_digest, get_algorithm, sec_key)
     end
     private :signed_info_builder
 
diff --git a/lib/saml_idp/signature_builder.rb b/lib/saml_idp/signature_builder.rb
index 83183f23..ed68a186 100644
--- a/lib/saml_idp/signature_builder.rb
+++ b/lib/saml_idp/signature_builder.rb
@@ -2,9 +2,11 @@
 module SamlIdp
   class SignatureBuilder
     attr_accessor :signed_info_builder
+    attr_accessor :x509_certificate
 
-    def initialize(signed_info_builder)
+    def initialize(signed_info_builder, cert=nil)
       self.signed_info_builder = signed_info_builder
+      @x509_certificate = cert
     end
 
     def raw
@@ -21,7 +23,7 @@ def raw
     end
 
     def x509_certificate
-      SamlIdp.config.x509_certificate
+      (@x509_certificate || SamlIdp.config.x509_certificate)
       .to_s
       .gsub(/-----BEGIN CERTIFICATE-----/,"")
       .gsub(/-----END CERTIFICATE-----/,"")
diff --git a/lib/saml_idp/signed_info_builder.rb b/lib/saml_idp/signed_info_builder.rb
index 81380666..f9120f0b 100644
--- a/lib/saml_idp/signed_info_builder.rb
+++ b/lib/saml_idp/signed_info_builder.rb
@@ -23,10 +23,11 @@ class SignedInfoBuilder
     attr_accessor :digest_value
     attr_accessor :raw_algorithm
 
-    def initialize(reference_id, digest_value, raw_algorithm)
+    def initialize(reference_id, digest_value, raw_algorithm, sec_key=nil)
       self.reference_id = reference_id
       self.digest_value = digest_value
       self.raw_algorithm = raw_algorithm
+      @sec_key = sec_key
     end
 
     def raw
@@ -65,7 +66,7 @@ def clean_algorithm_name
     private :clean_algorithm_name
 
     def secret_key
-      SamlIdp.config.secret_key
+      @sec_key || SamlIdp.config.secret_key
     end
     private :secret_key