diff -uNr a/vtools/manifest b/vtools/manifest
--- a/vtools/manifest f0dd63123a8745028d31cb4db9674994382318cbdc7c613d9886bf55c1ceacd8b22a7a4d9573fcf09ef53363caf0942ce2bcb3183e04abd09be6981a38208b32
+++ b/vtools/manifest 330fa25a9dc07c74d18d1b5489b17b8234ff442d0e3cb527263bea3183d41c5323867175a48a86c55c081c1225d90bb00236cbfe9549474ef77afb85b6b6544b
@@ -16,3 +16,5 @@
 Vpatch tool support for "No newline at end of file" directive.
 2018-09-26 phf
 Ksum standalone keccak hasher
+2018-10-25 bvt
+Standalone temporary file generation code; creates temporary files in the vpatch work directory.
diff -uNr a/vtools/src/temporary_file.adb b/vtools/src/temporary_file.adb
--- a/vtools/src/temporary_file.adb false
+++ b/vtools/src/temporary_file.adb 4747969b6df8aa268419f3259a757d1fee33b8b4a7d440b8adfe07c7f6335060b533791908ff1f5022ecfb51708277a59b0876812c4343e17df1f3f0de0ea767
@@ -0,0 +1,71 @@
+with Bits; use Bits;
+with System; use System;
+with SMG_Keccak; use SMG_Keccak;
+
+package body Temporary_File is
+   -- Create a new file or exit when the file with specified name exists.
+   -- Use fopen(3) with "x" mode to create the file or error out if it
+   -- already exists.
+   subtype File_Ptr is System.Address;
+   subtype C_String is System.Address;
+
+   function fopen (Path: C_String;
+                   Mode: C_String) return File_Ptr;
+   pragma Import (C, fopen);
+
+   procedure fclose (Stream: File_Ptr);
+   pragma Import (C, fclose);
+
+   function Create_File_Exclusive(Path: String) return Boolean is
+      Fptr: File_Ptr;
+   begin
+      declare
+         XP : aliased String := Path & ASCII.NUL;
+         XM : aliased String := "wx" & ASCII.NUL;
+      begin
+         Fptr := fopen(XP'Address, XM'Address);
+      end;
+      if Fptr = System.Null_Address then
+         return False;
+      end if;
+      fclose(Fptr);
+      return True;
+   end Create_File_Exclusive;
+
+   -- Create a temporary file with a randomly generated name;
+   -- if the file with random component F exists, retry with
+   -- H(F) as a new random component.
+   Function Temporary_File(Path_Prefix: String;
+                           Seed: Bitstream) return String is
+      Hash: Bitstream(1..64*8);
+      Name_Ctx: Keccak_Context;
+
+      procedure Hash_Bitstream(Input: Bitstream) is
+      begin
+         KeccakBegin(Name_Ctx);
+         KeccakHash(Name_Ctx, Input);
+         KeccakEnd(Name_Ctx, Hash);
+      end Hash_Bitstream;
+   begin
+      Hash_Bitstream(Seed);
+      loop
+         declare
+            File_Name: String := Path_Prefix & ToHex(Hash);
+         begin
+            if Create_File_Exclusive(File_Name) then
+               return File_Name;
+            end if;
+         end;
+         Hash_Bitstream(Hash);
+      end loop;
+   end Temporary_File;
+
+   function Temporary_File(Path_Prefix: String;
+                           Seed: String) return String is
+      B: Bitstream(1..Seed'Length*8);
+   begin
+      ToBitstream(Seed, B);
+      return Temporary_File(Path_Prefix, B);
+   end Temporary_File;
+
+end Temporary_File;
diff -uNr a/vtools/src/temporary_file.ads b/vtools/src/temporary_file.ads
--- a/vtools/src/temporary_file.ads false
+++ b/vtools/src/temporary_file.ads 94160eed9e9d4daf0b80dea4cc22b8060554e972e84b072ef7b5227dbcde4f5b0367c0706a6885a00f1151a59039a94db196370dfcbe941e352ac8838ea3a03e
@@ -0,0 +1,3 @@
+package Temporary_File is
+   function Temporary_File(Path_Prefix: String; Seed: String) return String;
+end Temporary_File;
diff -uNr a/vtools/src/vpatch.adb b/vtools/src/vpatch.adb
--- a/vtools/src/vpatch.adb 548d5a8f4f97e8cbfe84822335672c485b6e713e0e1620f706464090e75a1850c059e681c0d35edd23c444cac55d8ecd5180a53f6b570c46c632c4c34a7bee99
+++ b/vtools/src/vpatch.adb 2698cfb2456be817451e0e79abb76d94adf9f5a0befad34a52ed91d15342cd57e229b0f2a76f5f1da8b7f8824bedb7ef42d1832aaea71e2405d012f6e344da7e
@@ -1,6 +1,4 @@
 with Bits; use Bits;
-with Interfaces.C;
-with Interfaces.C.Strings;
 with Ada.Text_IO;  use Ada.Text_IO;
 with Ada.Integer_Text_IO; use  Ada.Integer_Text_IO;
 with Character_IO; use Character_IO;
@@ -11,6 +9,7 @@
 with Ada.Characters.Latin_1;
 with Ada.Sequential_IO;
 with SMG_Keccak; use SMG_Keccak;
+with Temporary_File; use Temporary_File;
 
 procedure VPatch is
    package Latin_1 renames Ada.Characters.Latin_1;
@@ -59,36 +58,22 @@
 
    -- Temporary File
 
-   procedure MkTemp(Template: Interfaces.C.Strings.Chars_Ptr);
-   pragma Import(C, mktemp);
-
-   function Temp_File_Name(Template: String) return String is
-      X: Interfaces.C.Strings.Chars_Ptr
-        := Interfaces.C.Strings.New_String(Template);
-   begin
-      MkTemp(X);
-      declare
-         Result: String := Interfaces.C.Strings.Value(X);
-      begin
-         Interfaces.C.Strings.Free(X);
-         return Result;
-      end;
-   end;
-
    procedure Create_Temp(File : in out File_Type;
                          Mode : in File_Mode := Out_File;
-                         Template : in String := "vpatch.XXX";
+                         Prefix : in String;
+                         Seed : in String := "";
                          Form : in String := "") is
-      Name: String := Temp_File_Name(Template);
+      Name: String := Temporary_File.Temporary_File(Prefix, Seed);
    begin
       Create(File, Mode, Name, Form);
    end;
 
    procedure Create_Temp(File : in out CIO.File_Type;
                          Mode : in CIO.File_Mode := CIO.Out_File;
-                         Template : in String := "vpatch.XXX";
+                         Prefix : in String;
+                         Seed : in String := "";
                          Form : in String := "") is
-      Name: String := Temp_File_Name(Template);
+      Name: String := Temporary_File.Temporary_File(Prefix, Seed);
    begin
       Create(File, Mode, Name, Form);
    end;
@@ -466,7 +451,7 @@
 
       -- prepare keccak and open files
       KeccakBegin(To_Ctx);
-      Create_Temp(To_F, Template => "tmp.XXX");
+      Create_Temp(To_F, Prefix => "vpatch-", Seed => To_F_Name);
       case Op is
          when Op_Create =>
             Has_Input_File := False;