unity Facebook For Android Error

Hello guys i am still in the beginning to import Facebook SDK to my game i just want to make the player share his\her score on facebook by press a button so i just in the early steps and suddenly that error come to me what is it meaning and how ti solve it thanks in Advance

The complete Error message :

Win32Exception: ApplicationName='cmd', CommandLine='/Cecho "xxx" | openssl base64', CurrentDirectory='' System.Diagnostics.Process.Start_noshell (System.Diagnostics.ProcessStartInfo startInfo, System.Diagnostics.Process process) System.Diagnostics.Process.Start_common (System.Diagnostics.ProcessStartInfo startInfo, System.Diagnostics.Process process) System.Diagnostics.Process.Start () (wrapper remoting-invoke-with-check) System.Diagnostics.Process:Start () UnityEditor.FacebookEditor.FacebookAndroidUtil.DoesCommandExist (System.String command) (at Assets/Facebook/Editor/android/FacebookAndroidUtil.cs:164) UnityEditor.FacebookEditor.FacebookAndroidUtil.get_DebugKeyHash () (at Assets/Facebook/Editor/android/FacebookAndroidUtil.cs:66) UnityEditor.FacebookEditor.FacebookAndroidUtil.get_SetupProperly () (at Assets/Facebook/Editor/android/FacebookAndroidUtil.cs:44) Facebook.Unity.Editor.FacebookSettingsEditor.AndroidUtilGUI () (at Assets/Facebook/Editor/FacebookSettingsEditor.cs:178) Facebook.Unity.Editor.FacebookSettingsEditor.OnInspectorGUI () (at Assets/Facebook/Editor/FacebookSettingsEditor.cs:63) UnityEditor.InspectorWindow.DrawEditor (UnityEditor.Editor editor, Int32 editorIndex, Boolean rebuildOptimizedGUIBlock, System.Boolean& showImportedObjectBarNext, UnityEngine.Rect& importedObjectBarRect) (at C:/buildslave/unity/build/Editor/Mono/Inspector/InspectorWindow.cs:1235) UnityEditor.DockArea:OnGUI()