diff --git a/Makefile b/Makefile
index 6fff585c..b0b29563 100644
--- a/Makefile
+++ b/Makefile
@@ -66,7 +66,7 @@ protoc:
 	@for f in `find . -type f -name '*.proto' -not -path './vendor/*'`; do \
 		echo "⇒ Processing $$f "; \
 		protoc \
-			--proto_path=.:./vendor:./vendor/github.com/nspcc-dev/neofs-api-go:/usr/local/include \
+			--proto_path=.:./vendor:./vendor/github.com/nspcc-dev/neofs-api-go:/usr/local/include:./pkg/services/private \
 			--gofast_out=plugins=grpc,paths=source_relative:. $$f; \
 	done
 	rm -rf vendor
diff --git a/go.mod b/go.mod
index f0501e41..8a322371 100644
--- a/go.mod
+++ b/go.mod
@@ -5,6 +5,7 @@ go 1.14
 require (
 	code.cloudfoundry.org/bytefmt v0.0.0-20200131002437-cf55d5288a48
 	github.com/alecthomas/participle v0.6.0
+	github.com/golang/protobuf v1.4.3
 	github.com/google/uuid v1.1.1
 	github.com/hashicorp/golang-lru v0.5.4
 	github.com/klauspost/compress v1.11.3
diff --git a/go.sum b/go.sum
index 29b9824f..402a5840 100644
Binary files a/go.sum and b/go.sum differ
diff --git a/pkg/services/private/service.pb.go b/pkg/services/private/service.pb.go
new file mode 100644
index 00000000..3c12c3fb
Binary files /dev/null and b/pkg/services/private/service.pb.go differ
diff --git a/pkg/services/private/service.proto b/pkg/services/private/service.proto
new file mode 100644
index 00000000..23a569fa
--- /dev/null
+++ b/pkg/services/private/service.proto
@@ -0,0 +1,41 @@
+syntax = "proto3";
+
+package private;
+
+import "types.proto";
+
+option go_package = "github.com/nspcc-dev/neofs-node/pkg/services/private";
+
+// `PrivateService` provides an interface for internal work with the storage node.
+service PrivateService {
+    // Performs health check of the storage node.
+    rpc HealthCheck (HealthCheckRequest) returns (HealthCheckResponse);
+}
+
+// Health check request.
+message HealthCheckRequest {
+    // Health check request body.
+    message Body {
+    }
+
+    // Body of health check request message.
+    Body body = 1;
+
+    // Body signature.
+    Signature signature = 2;
+}
+
+// Health check request.
+message HealthCheckResponse {
+    // Health check response body
+    message Body {
+        // Health status of storage node.
+        HealthStatus status = 1;
+    }
+
+    // Body of health check response message.
+    Body body = 1;
+
+    // Body signature.
+    Signature signature = 2;
+}
diff --git a/pkg/services/private/types.pb.go b/pkg/services/private/types.pb.go
new file mode 100644
index 00000000..373446f1
Binary files /dev/null and b/pkg/services/private/types.pb.go differ
diff --git a/pkg/services/private/types.proto b/pkg/services/private/types.proto
new file mode 100644
index 00000000..f473bb7c
--- /dev/null
+++ b/pkg/services/private/types.proto
@@ -0,0 +1,26 @@
+syntax = "proto3";
+
+package private;
+
+option go_package = "github.com/nspcc-dev/neofs-node/pkg/services/private";
+
+// Signature of some message.
+message Signature {
+    // Public key used for signing.
+    bytes key = 1 [json_name = "key"];
+
+    // Binary signature.
+    bytes sign = 2 [json_name = "signature"];
+}
+
+// Health status of the storage node.
+enum HealthStatus {
+    // Undefined status, default value.
+    STATUS_UNDEFINED = 0;
+
+    // Node is online.
+    ONLINE = 1;
+
+    // Node is offline.
+    OFFLINE = 2;
+}