diff --git a/state/sign.go b/state/sign.go
new file mode 100644
index 0000000..c0d4c7f
--- /dev/null
+++ b/state/sign.go
@@ -0,0 +1,8 @@
+package state
+
+// SignedData returns payload bytes of the request.
+//
+// Always returns empty slice.
+func (m NetmapRequest) SignedData() ([]byte, error) {
+	return make([]byte, 0), nil
+}
diff --git a/state/sign_test.go b/state/sign_test.go
new file mode 100644
index 0000000..8f9a98f
--- /dev/null
+++ b/state/sign_test.go
@@ -0,0 +1,62 @@
+package state
+
+import (
+	"testing"
+
+	"github.com/nspcc-dev/neofs-api-go/service"
+	"github.com/nspcc-dev/neofs-crypto/test"
+	"github.com/stretchr/testify/require"
+)
+
+func TestRequestSign(t *testing.T) {
+	sk := test.DecodeKey(0)
+
+	type sigType interface {
+		service.SignedDataWithToken
+		service.SignKeyPairAccumulator
+		service.SignKeyPairSource
+		SetToken(*service.Token)
+	}
+
+	items := []struct {
+		constructor    func() sigType
+		payloadCorrupt []func(sigType)
+	}{
+		{ // NetmapRequest
+			constructor: func() sigType {
+				return new(NetmapRequest)
+			},
+		},
+	}
+
+	for _, item := range items {
+		{ // token corruptions
+			v := item.constructor()
+
+			token := new(service.Token)
+			v.SetToken(token)
+
+			require.NoError(t, service.SignDataWithSessionToken(sk, v))
+
+			require.NoError(t, service.VerifyAccumulatedSignaturesWithToken(v))
+
+			token.SetSessionKey(append(token.GetSessionKey(), 1))
+
+			require.Error(t, service.VerifyAccumulatedSignaturesWithToken(v))
+		}
+
+		{ // payload corruptions
+			for _, corruption := range item.payloadCorrupt {
+				v := item.constructor()
+
+				require.NoError(t, service.SignDataWithSessionToken(sk, v))
+
+				require.NoError(t, service.VerifyAccumulatedSignaturesWithToken(v))
+
+				corruption(v)
+
+				require.Error(t, service.VerifyAccumulatedSignaturesWithToken(v))
+			}
+		}
+	}
+}