diff -uNr a/vtools/manifest b/vtools/manifest
--- a/vtools/manifest 7896d8cc732aef7cbaae1c872dd824f51c5f6d1d23e42bb57ce03cf7b84664cc2140d4dbb9c70b72e14a1f82a59acdda3b7432e90423f0a8e93cf4fe5abf2e7f
+++ b/vtools/manifest de81a97d5da86b1a3f934e6afb04b4ab40aa58163ad292438814fd9ca1dc09d9209c4984099e2e709fbe637cf8046a30b04039e2abce74ec565bf2f7881c0e91
@@ -2,3 +2,4 @@
 511300 phf vdiff_fixes_newline_gcc Fixes for C99 compatability, support for "No newline at end of file" directive.
 511300 phf keccak Included diana_coman's keccak implementation.
 511300 phf vdiff_keccak Vdiff hashing and output using Keccak instead of SHA512.
+512600 phf vtools_fixes_bitrate_char_array Fixes for keccak from diana_coman, different approach to C interop.
diff -uNr a/vtools/src/keccak_c.adb b/vtools/src/keccak_c.adb
--- a/vtools/src/keccak_c.adb 680efb9458a976f700a689a6b0678510172945e94d35207f07bea280bb87b30edc889968fbf6c922c8cc5c79b9193986ab66037cc36f47d52b49e91826c22fe4
+++ b/vtools/src/keccak_c.adb 252a6f237724580f4af2f1fbf2dff39dcdd7c1a14ac7c17021d4ed0d0939f6394bf2cbce3e2ecc3261b8474ecf0d7de34728467679e557a7c44bad510d070747
@@ -54,28 +54,41 @@
    end C_Begin;
 
    procedure C_Hash(Ctx: in C_Context_Access;
-                    Input: Interfaces.C.Char_Array;
-                    Len: Interfaces.C.Size_T) is
+                    Input: Char_Star;
+                    Len: Interfaces.C.size_t) is
       L: Natural := Natural(Len);
       S: String(1..L);
       B: Bitstream(1..S'Length*8);
+      Ptr: Char_Star := Input;
    begin
-      Interfaces.C.To_Ada(Input, S, L, Trim_Nul => False);
+      if Input = null then
+         raise C.Strings.Dereference_Error;
+      end if;
+      for Chr of S loop
+         Chr := Character(Ptr.all);
+         Char_Ptrs.Increment(Ptr);
+      end loop;
       ToBitstream(S, B);
       KeccakHash(Ctx.all, B);
    end C_Hash;
 
    procedure C_End(Ctx: C_Context_Access;
-                   Output: out Interfaces.C.Char_Array;
+                   Output: Char_Star;
                    Len: Interfaces.C.Size_T) is
       L: Natural := Natural(Len);
       S: String(1..L);
       B: Bitstream(1..S'Length*8);
-      Count: Interfaces.C.Size_T;
+      Ptr: Char_Star := Output;
    begin
+      if Output = null then
+         raise C.Strings.Dereference_Error;
+      end if;
       KeccakEnd(Ctx.all, B);
       ToString(B, S);
-      Interfaces.C.To_C(S, Output(0..Len), Count, Append_Nul => False);
+      for Chr of S loop
+         Ptr.all := Interfaces.C.char(Chr);
+         Char_Ptrs.Increment(Ptr);
+      end loop;
       -- Len = Count
    end C_End;
 
diff -uNr a/vtools/src/keccak_c.ads b/vtools/src/keccak_c.ads
--- a/vtools/src/keccak_c.ads 33d0a8bfac503d941796252636419dfbc9917d9d67c2e15e13e85083afb8ed46cde57452b61ef275ccfde07b7891d510467b49868882248a5836bce52ef7a7d0
+++ b/vtools/src/keccak_c.ads 9e720f186b11bb3e2d398765619e1e4220659e74bdf9ad4d3be83eeb51c9a45e5f7a4bfcece333f5e86b50838874dbc31462efd45f25294c3661eb069c9e4db2
@@ -1,8 +1,17 @@
 with Interfaces; use Interfaces;
 with Interfaces.C; use Interfaces.C;
+with Interfaces.C.Strings;
+with Interfaces.C.Pointers;
 with Ada.Unchecked_Deallocation;
 with SMG_Keccak; use SMG_Keccak;
 package Keccak_C is
+   package Char_Ptrs is
+      new Interfaces.C.Pointers (Index              => size_t,
+                                 Element            => char,
+                                 Element_Array      => char_array,
+                                 Default_Terminator => nul);
+   use type Char_Ptrs.Pointer;
+   subtype Char_Star is Char_Ptrs.Pointer;
    subtype C_Context is Keccak_Context(Block_Len=>Default_Bitrate);
    type C_Context_Access is access C_Context;
    procedure C_Get_Size(Size: out Interfaces.C.size_t);
@@ -10,11 +19,11 @@
    function C_Begin return C_Context_Access;
    pragma Export (C, C_Begin, "keccak_begin");
    procedure C_Hash(Ctx: C_Context_Access;
-                    Input: Interfaces.C.Char_Array;
+                    Input: Char_Star;
                     Len: Interfaces.C.Size_T);
    pragma Export (C, C_Hash, "keccak_hash");
    procedure C_End(Ctx: C_Context_Access;
-                   Output: out Interfaces.C.Char_Array;
+                   Output: Char_Star;
                    Len: Interfaces.C.Size_T);
    pragma Export (C, C_End, "keccak_end");
    procedure C_Deallocate(Ctx: in out C_Context_Access);
diff -uNr a/vtools/src/smg_keccak.adb b/vtools/src/smg_keccak.adb
--- a/vtools/src/smg_keccak.adb 8f038c226bd823b585a5081adbdbbf6a394c552875346ab9474c3a7679a8f7636704eb3230f0588fb250fb3a45d584e68a1de7fe92ee209c91d2cdaa0fe3e217
+++ b/vtools/src/smg_keccak.adb b45b24d4e1024ed3c006f3b1754cea63cb7dd34ba653e3ad017bb54800d4b43c5283e7fba95c434d8f7fe470118c2137da999d55a6335bd80be7491ad7fdca92
@@ -217,7 +217,7 @@
       ToPos := Block'Last;
       FromPos := ToPos - SBB + 1;
       BWord := (others => 0);
-      BWord(Bitword'First .. Bitword'First + SBB - 1) := Block(ToPos..FromPos);
+      BWord(Bitword'First .. Bitword'First + SBB - 1) := Block(FromPos..ToPos);
       Word := BitsToWord( BWord );
       S( X, Y ) := S( X, Y ) xor Word;
     end if;