diff --git a/SecurityPkg/Tcg/Opal/OpalPasswordDxe/OpalDriver.c b/SecurityPkg/Tcg/Opal/OpalPasswordDxe/OpalDriver.c
index 3764b24344..9bf1ced3cc 100644
--- a/SecurityPkg/Tcg/Opal/OpalPasswordDxe/OpalDriver.c
+++ b/SecurityPkg/Tcg/Opal/OpalPasswordDxe/OpalDriver.c
@@ -239,7 +239,7 @@ OpalDriverPopUpHddPassword (
     return NULL;
   }
 
-  UnicodeStrToAsciiStr(Unicode, Ascii);
+  UnicodeStrToAsciiStrS (Unicode, Ascii, MAX_PASSWORD_SIZE + 1);
 
   return Ascii;
 }
@@ -616,7 +616,7 @@ OpalDriverGetDeviceNameByProtocol(
         ASSERT (Dev->Name16 != NULL);
         StrCpyS (Dev->Name16, StrLength, DevName);
         Dev->NameZ = (CHAR8*)AllocateZeroPool(StrLength);
-        UnicodeStrToAsciiStr(DevName, Dev->NameZ);
+        UnicodeStrToAsciiStrS (DevName, Dev->NameZ, StrLength);
 
         //
         // Retrieve bridge BDF info and port number or namespace depending on type
diff --git a/SecurityPkg/Tcg/Opal/OpalPasswordDxe/OpalHii.c b/SecurityPkg/Tcg/Opal/OpalPasswordDxe/OpalHii.c
index 7a4b872048..9a44c5697e 100644
--- a/SecurityPkg/Tcg/Opal/OpalPasswordDxe/OpalHii.c
+++ b/SecurityPkg/Tcg/Opal/OpalPasswordDxe/OpalHii.c
@@ -600,7 +600,7 @@ HiiPsidRevert(
 
   OpalHiiGetBrowserData();
 
-  UnicodeStrToAsciiStr(gHiiConfiguration.Psid, (CHAR8*)Psid.Psid);
+  UnicodeStrToAsciiStrS (gHiiConfiguration.Psid, (CHAR8*)Psid.Psid, PSID_CHARACTER_LENGTH);
 
   OpalDisk = HiiGetOpalDiskCB (gHiiConfiguration.SelectedDiskIndex);
   if (OpalDisk != NULL) {
@@ -1049,7 +1049,7 @@ HiiPasswordEntered(
     return EFI_BUFFER_TOO_SMALL;
   }
 
-  UnicodeStrToAsciiStr(UniStr, Password);
+  UnicodeStrToAsciiStrS (UniStr, Password, sizeof (Password));
   gBS->FreePool(UniStr);
 
   if (gHiiConfiguration.SelectedAction == HII_KEY_ID_GOTO_UNLOCK) {
@@ -1288,7 +1288,7 @@ HiiSetFormString(
   //
   // Copy into unicode string, then copy into string id
   //
-  AsciiStrToUnicodeStr( SrcAsciiStr, UniStr );
+  AsciiStrToUnicodeStrS ( SrcAsciiStr, UniStr, Len + 1);
 
   //
   // Update the string in the form
diff --git a/SecurityPkg/Tcg/Opal/OpalPasswordDxe/OpalHiiPrivate.h b/SecurityPkg/Tcg/Opal/OpalPasswordDxe/OpalHiiPrivate.h
index 366cd3813e..bb086bd35f 100644
--- a/SecurityPkg/Tcg/Opal/OpalPasswordDxe/OpalHiiPrivate.h
+++ b/SecurityPkg/Tcg/Opal/OpalPasswordDxe/OpalHiiPrivate.h
@@ -53,7 +53,7 @@ typedef struct {
 * The type indicates the structure of the PSID authority
 */
 typedef struct {
-    UINT8 Psid[32];
+    UINT8 Psid[PSID_CHARACTER_LENGTH];
 } TCG_PSID;
 
 /**