diff --git a/projects/ucap-webmessenger-app/src/app/layouts/common/dialogs/file-viewer.dialog.component.ts b/projects/ucap-webmessenger-app/src/app/layouts/common/dialogs/file-viewer.dialog.component.ts
index aa49b093..489bd5fc 100644
--- a/projects/ucap-webmessenger-app/src/app/layouts/common/dialogs/file-viewer.dialog.component.ts
+++ b/projects/ucap-webmessenger-app/src/app/layouts/common/dialogs/file-viewer.dialog.component.ts
@@ -1,10 +1,4 @@
-import {
-  Component,
-  OnInit,
-  OnDestroy,
-  Inject,
-  EventEmitter
-} from '@angular/core';
+import { Component, OnInit, OnDestroy, Inject } from '@angular/core';
 
 import { MatDialogRef, MAT_DIALOG_DATA } from '@angular/material';
 import { NGXLogger } from 'ngx-logger';
@@ -20,6 +14,7 @@ import {
 import { FileDownloadItem } from '@ucap-webmessenger/api';
 import { CommonApiService } from '@ucap-webmessenger/api-common';
 import { TranslateService } from '@ngx-translate/core';
+import { FileProtocolService } from '@ucap-webmessenger/protocol-file';
 
 export interface FileViewerDialogData {
   fileInfo: FileEventJson;
@@ -55,6 +50,7 @@ export class FileViewerDialogComponent implements OnInit, OnDestroy {
     private translateService: TranslateService,
     private snackBarService: SnackBarService,
     private commonApiService: CommonApiService,
+    private fileProtocolService: FileProtocolService,
     private logger: NGXLogger
   ) {
     this.fileInfo = data.fileInfo;
@@ -98,6 +94,14 @@ export class FileViewerDialogComponent implements OnInit, OnDestroy {
 
           FileUtil.fromBlobToBuffer(blob)
             .then(buffer => {
+              /** download check */
+              this.fileProtocolService
+                .downCheck({
+                  seq: this.fileInfo.attachmentSeq
+                })
+                .pipe(take(1))
+                .subscribe();
+
               this.nativeService
                 .saveFile(buffer, this.fileInfo.fileName, mimeType)
                 .then(result => {
diff --git a/projects/ucap-webmessenger-app/src/app/layouts/messenger/components/messages.component.ts b/projects/ucap-webmessenger-app/src/app/layouts/messenger/components/messages.component.ts
index 4f6080b5..55374a17 100644
--- a/projects/ucap-webmessenger-app/src/app/layouts/messenger/components/messages.component.ts
+++ b/projects/ucap-webmessenger-app/src/app/layouts/messenger/components/messages.component.ts
@@ -117,6 +117,7 @@ import { NativeService, UCAP_NATIVE_SERVICE } from '@ucap-webmessenger/native';
 import { TranslateService } from '@ngx-translate/core';
 import { TranslatePipe } from 'projects/ucap-webmessenger-ui/src/lib/pipes/translate.pipe';
 import { TranslateService as uiTranslateService } from '@ucap-webmessenger/ui';
+import { FileProtocolService } from '@ucap-webmessenger/protocol-file';
 
 @Component({
   selector: 'app-layout-messenger-messages',
@@ -216,6 +217,7 @@ export class MessagesComponent implements OnInit, OnDestroy, AfterViewInit {
     private sessionStorageService: SessionStorageService,
     private localStorageService: LocalStorageService,
     private commonApiService: CommonApiService,
+    private fileProtocolService: FileProtocolService,
     private clipboardService: ClipboardService,
     private uiTranslateService: uiTranslateService,
     private translateService: TranslateService,
@@ -1021,6 +1023,13 @@ export class MessagesComponent implements OnInit, OnDestroy, AfterViewInit {
 
           FileUtil.fromBlobToBuffer(blob)
             .then(buffer => {
+              /** download check */
+              this.fileProtocolService.downCheck({
+                seq: value.fileInfo.attachmentSeq
+              })
+                .pipe(take(1))
+                .subscribe();
+
               this.nativeService
                 .saveFile(buffer, value.fileInfo.fileName, mimeType, savePath)
                 .then(result => {
diff --git a/projects/ucap-webmessenger-app/src/app/layouts/messenger/components/right-drawer/album-box.component.ts b/projects/ucap-webmessenger-app/src/app/layouts/messenger/components/right-drawer/album-box.component.ts
index 7abc2530..f5045111 100644
--- a/projects/ucap-webmessenger-app/src/app/layouts/messenger/components/right-drawer/album-box.component.ts
+++ b/projects/ucap-webmessenger-app/src/app/layouts/messenger/components/right-drawer/album-box.component.ts
@@ -2,14 +2,15 @@ import { Component, OnInit, OnDestroy, Inject } from '@angular/core';
 import {
   FileInfo,
   FileDownloadInfo,
-  FileType
+  FileType,
+  FileProtocolService
 } from '@ucap-webmessenger/protocol-file';
 import { Subscription, combineLatest } from 'rxjs';
 import { Store, select } from '@ngrx/store';
 
 import * as AppStore from '@app/store';
 import { tap, map, take, finalize } from 'rxjs/operators';
-import { FileUtil, MimeUtil, DeviceType } from '@ucap-webmessenger/core';
+import { FileUtil, MimeUtil } from '@ucap-webmessenger/core';
 import { CommonApiService } from '@ucap-webmessenger/api-common';
 import { LoginResponse } from '@ucap-webmessenger/protocol-authentication';
 import { SessionStorageService } from '@ucap-webmessenger/web-storage';
@@ -65,6 +66,7 @@ export class AlbumBoxComponent implements OnInit, OnDestroy {
     private store: Store<any>,
     private sessionStorageService: SessionStorageService,
     private commonApiService: CommonApiService,
+    private fileProtocolService: FileProtocolService,
     private translateService: TranslateService,
     private snackBarService: SnackBarService,
     @Inject(UCAP_NATIVE_SERVICE) private nativeService: NativeService,
@@ -232,6 +234,14 @@ export class AlbumBoxComponent implements OnInit, OnDestroy {
 
           FileUtil.fromBlobToBuffer(blob)
             .then(buffer => {
+              /** download check */
+              this.fileProtocolService
+                .downCheck({
+                  seq: fileInfo.info.seq
+                })
+                .pipe(take(1))
+                .subscribe();
+
               this.nativeService
                 .saveFile(buffer, fileInfo.info.name, mimeType)
                 .then(result => {
diff --git a/projects/ucap-webmessenger-app/src/app/layouts/messenger/components/right-drawer/file-box.component.ts b/projects/ucap-webmessenger-app/src/app/layouts/messenger/components/right-drawer/file-box.component.ts
index 93383516..54ae3229 100644
--- a/projects/ucap-webmessenger-app/src/app/layouts/messenger/components/right-drawer/file-box.component.ts
+++ b/projects/ucap-webmessenger-app/src/app/layouts/messenger/components/right-drawer/file-box.component.ts
@@ -3,7 +3,8 @@ import { MatPaginator, MatTableDataSource, MatSort } from '@angular/material';
 import {
   FileInfo,
   FileDownloadInfo,
-  FileType
+  FileType,
+  FileProtocolService
 } from '@ucap-webmessenger/protocol-file';
 import { Subscription, combineLatest } from 'rxjs';
 import { Store, select } from '@ngrx/store';
@@ -11,7 +12,7 @@ import { Store, select } from '@ngrx/store';
 import * as AppStore from '@app/store';
 import * as EventStore from '@app/store/messenger/event';
 import { tap, map, take, finalize } from 'rxjs/operators';
-import { FileUtil, MimeUtil, DeviceType } from '@ucap-webmessenger/core';
+import { FileUtil, MimeUtil } from '@ucap-webmessenger/core';
 import { LoginResponse } from '@ucap-webmessenger/protocol-authentication';
 import { SessionStorageService } from '@ucap-webmessenger/web-storage';
 import { KEY_LOGIN_RES_INFO } from '@app/types/login-res-info.type';
@@ -78,6 +79,7 @@ export class FileBoxComponent implements OnInit, OnDestroy {
     private store: Store<any>,
     private sessionStorageService: SessionStorageService,
     private commonApiService: CommonApiService,
+    private fileProtocolService: FileProtocolService,
     private translateService: TranslateService,
     private snackBarService: SnackBarService,
     @Inject(UCAP_NATIVE_SERVICE) private nativeService: NativeService,
@@ -275,6 +277,14 @@ export class FileBoxComponent implements OnInit, OnDestroy {
 
           FileUtil.fromBlobToBuffer(blob)
             .then(buffer => {
+              /** download check */
+              this.fileProtocolService
+                .downCheck({
+                  seq: fileInfo.info.seq
+                })
+                .pipe(take(1))
+                .subscribe();
+
               this.nativeService
                 .saveFile(buffer, fileInfo.info.name, mimeType)
                 .then(result => {
diff --git a/projects/ucap-webmessenger-protocol-file/src/lib/protocols/down-check.ts b/projects/ucap-webmessenger-protocol-file/src/lib/protocols/down-check.ts
index 8aee32d6..38cb9706 100644
--- a/projects/ucap-webmessenger-protocol-file/src/lib/protocols/down-check.ts
+++ b/projects/ucap-webmessenger-protocol-file/src/lib/protocols/down-check.ts
@@ -25,7 +25,7 @@ export const encodeDownCheck: ProtocolEncoder<DownCheckRequest> = (
 ) => {
   const bodyList: PacketBody[] = [];
 
-  bodyList.push({ type: PacketBodyValue.Integer, value: req.seq });
+  bodyList.push({ type: PacketBodyValue.String, value: req.seq });
   return bodyList;
 };