diff --git a/crypto.go b/crypto.go
index 1a2c590..cc2f92e 100644
--- a/crypto.go
+++ b/crypto.go
@@ -7,7 +7,6 @@ import (
 	"crypto/sha256"
 	"encoding/hex"
 	"encoding/json"
-	"errors"
 	"golang.org/x/crypto/blowfish"
 	"io"
 )
@@ -16,7 +15,20 @@ type BaseMessage struct {
 	Signature string
 }
 
-func DecryptAndVerify(input []byte, key *rsa.PrivateKey, pub *rsa.PublicKey, signature []byte, v interface{}) error {
+func (it *BaseMessage) GetSignature() string {
+	return it.Signature
+}
+
+func (it *BaseMessage) SetSignature(sig string) {
+	it.Signature = sig
+}
+
+type Message interface {
+	SetSignature(sig string)
+	GetSignature() string
+}
+
+func DecryptAndVerify(input []byte, key *rsa.PrivateKey, pub *rsa.PublicKey, signature []byte, v Message) error {
 	all, err := hex.DecodeString(string(input))
 	if err != nil {
 		return err
@@ -49,12 +61,7 @@ func DecryptAndVerify(input []byte, key *rsa.PrivateKey, pub *rsa.PublicKey, sig
 		return err
 	}
 
-	baseReq, ok := v.(*BaseMessage)
-	if !ok {
-		return errors.New("non-base request")
-	}
-
-	recvSignature, err := hex.DecodeString(baseReq.Signature)
+	recvSignature, err := hex.DecodeString(v.GetSignature())
 	if err != nil {
 		return err
 	}
@@ -65,7 +72,7 @@ func DecryptAndVerify(input []byte, key *rsa.PrivateKey, pub *rsa.PublicKey, sig
 	return err
 }
 
-func EncryptAndSign(v interface{}, key *rsa.PrivateKey, pub *rsa.PublicKey, signature []byte, writer io.Writer) error {
+func EncryptAndSign(v Message, key *rsa.PrivateKey, pub *rsa.PublicKey, signature []byte, writer io.Writer) error {
 	passwordAndIV := make([]byte, 40)
 	_, err := rand.Read(passwordAndIV)
 	if err != nil {
@@ -96,11 +103,7 @@ func EncryptAndSign(v interface{}, key *rsa.PrivateKey, pub *rsa.PublicKey, sign
 		return err
 	}
 
-	sign, ok := v.(*BaseMessage)
-	if !ok {
-		return errors.New("given message can't be signed")
-	}
-	sign.Signature = hex.EncodeToString(plainSignature)
+	v.SetSignature(hex.EncodeToString(plainSignature))
 
 	body, err := json.Marshal(v)
 
diff --git a/crypto_test.go b/crypto_test.go
index 71032cf..3dae43e 100644
--- a/crypto_test.go
+++ b/crypto_test.go
@@ -28,7 +28,10 @@ func TestSingleRound(t *testing.T) {
 	keyA, _ := rsa.GenerateKey(rand.Reader, 4096)
 	keyB, _ := rsa.GenerateKey(rand.Reader, 4096)
 	signature := []byte("Hello world!")
-	v := &service.BaseMessage{}
+	v := &service.UpdateOpenVPNConfigRequest{
+		BaseMessage: &service.BaseMessage{""},
+		Config:      "Hello world!",
+	}
 	x := make([]byte, 0)
 	b := bytes.NewBuffer(x)
 	err := service.EncryptAndSign(v, keyA, &keyB.PublicKey, signature, b)
@@ -37,9 +40,16 @@ func TestSingleRound(t *testing.T) {
 		t.Errorf("Failed encrypting: %s", err)
 	}
 
-	err = service.DecryptAndVerify(b.Bytes(), keyB, &keyA.PublicKey, signature, &service.BaseMessage{})
+	ov := &service.UpdateOpenVPNConfigRequest{
+		BaseMessage: &service.BaseMessage{""},
+	}
+	err = service.DecryptAndVerify(b.Bytes(), keyB, &keyA.PublicKey, signature, ov)
 
 	if err != nil {
 		t.Errorf("Failed decrypting: %s", err)
 	}
+
+	if ov.Config != "Hello world!" {
+		t.Errorf("Config scrambled: %s", ov.Config)
+	}
 }
diff --git a/http.go b/http.go
index c25a463..057b9e5 100644
--- a/http.go
+++ b/http.go
@@ -21,22 +21,22 @@ type HttpServer struct {
 }
 
 type CreateCSRRequest struct {
-	BaseMessage
+	*BaseMessage
 	Hostname string
 }
 
 type CreateCSRResponse struct {
-	BaseMessage
+	*BaseMessage
 	CSR string `json:"csr"`
 }
 
 type UpdateOpenVPNConfigRequest struct {
-	BaseMessage
+	*BaseMessage
 	Config string
 }
 
 type DeliverCertificateRequest struct {
-	BaseMessage
+	*BaseMessage
 	Certificate string
 }
 
@@ -53,7 +53,9 @@ func (it *HttpServer) Start() {
 
 	http.HandleFunc("/create-csr", func(writer http.ResponseWriter, request *http.Request) {
 		log.Printf("%s /create-csr", strings.ToUpper(request.Method))
-		req := &CreateCSRRequest{}
+		req := &CreateCSRRequest{
+			BaseMessage: &BaseMessage{""},
+		}
 		err := it.verifyRequest(request, req)
 
 		if err != nil {
@@ -69,13 +71,16 @@ func (it *HttpServer) Start() {
 		}
 
 		it.writeResponse(writer, CreateCSRResponse{
-			CSR: string(csr),
+			BaseMessage: &BaseMessage{""},
+			CSR:         string(csr),
 		})
 	})
 
 	http.HandleFunc("/deliver-crt", func(writer http.ResponseWriter, request *http.Request) {
 		log.Printf("%s /deliver-crt", strings.ToUpper(request.Method))
-		req := &DeliverCertificateRequest{}
+		req := &DeliverCertificateRequest{
+			BaseMessage: &BaseMessage{""},
+		}
 		err := it.verifyRequest(request, req)
 		if err != nil {
 			log.Printf("Error on %s %s: %s", request.Method, request.URL.Path, err)
@@ -94,7 +99,9 @@ func (it *HttpServer) Start() {
 
 	http.HandleFunc("/update-openvpn-config", func(writer http.ResponseWriter, request *http.Request) {
 		log.Printf("%s /update-openvpn-config", strings.ToUpper(request.Method))
-		req := &UpdateOpenVPNConfigRequest{}
+		req := &UpdateOpenVPNConfigRequest{
+			BaseMessage: &BaseMessage{""},
+		}
 		err := it.verifyRequest(request, req)
 		if err != nil {
 			log.Printf("Error on %s %s: %s", request.Method, request.URL.Path, err)
@@ -114,11 +121,11 @@ func (it *HttpServer) Start() {
 	http.ListenAndServe(":7864", nil)
 }
 
-func (it *HttpServer) writeResponse(writer http.ResponseWriter, v interface{}) error {
+func (it *HttpServer) writeResponse(writer http.ResponseWriter, v Message) error {
 	return EncryptAndSign(v, it.manager.privateKey, it.manager.CAPublicKey(), it.manager.GetServerFingerprint(), writer)
 }
 
-func (it *HttpServer) verifyRequest(r *http.Request, v interface{}) (error) {
+func (it *HttpServer) verifyRequest(r *http.Request, v Message) (error) {
 	hexBody, err := ioutil.ReadAll(r.Body)
 	if err != nil {
 		return err