diff --git a/harbour/ChangeLog b/harbour/ChangeLog
index 8291c66096..c66320f48a 100644
--- a/harbour/ChangeLog
+++ b/harbour/ChangeLog
@@ -16,6 +16,12 @@
    The license applies to all entries newer than 2009-04-28.
 */
 
+2010-06-22 17:28 UTC+0200 Viktor Szakats (harbour.01 syenar.hu)
+  * src/rtl/hbsha1.c
+  * src/rtl/hbsha1hm.c
+    + Added Win64 support for SHA1 functions.
+    ; Please review it.
+
 2010-06-22 17:00 UTC+0200 Viktor Szakats (harbour.01 syenar.hu)
   * src/macro/macro.yyc
   * src/macro/macro.y
diff --git a/harbour/src/rtl/hbsha1.c b/harbour/src/rtl/hbsha1.c
index 20e15fdb9c..e6a1799084 100644
--- a/harbour/src/rtl/hbsha1.c
+++ b/harbour/src/rtl/hbsha1.c
@@ -60,7 +60,37 @@ HB_FUNC( HB_SHA1 )
    SHA_CTX ctx;
 
    SHA1_Init( &ctx );
-   SHA1_Update( &ctx, hb_parcx( 1 ), hb_parclen( 1 ) );
+
+   #if HB_SIZE_MAX > UINT_MAX
+   {
+      const char * buffer = hb_parcx( 1 );
+      HB_SIZE nCount = hb_parclen( 1 );
+      HB_SIZE nDone = 0;
+
+      while( nCount )
+      {
+         unsigned int uiChunk;
+
+         if( nCount > ( HB_SIZE ) UINT_MAX )
+         {
+            uiChunk = UINT_MAX;
+            nCount -= ( HB_SIZE ) uiChunk;
+         }
+         else
+         {
+            uiChunk = ( unsigned int ) nCount;
+            nCount = 0;
+         }
+
+         SHA1_Update( &ctx, buffer + nDone, uiChunk );
+
+         nDone += ( HB_SIZE ) uiChunk;
+      }
+   }
+   #else
+      SHA1_Update( &ctx, hb_parcx( 1 ), hb_parclen( 1 ) );
+   #endif
+
    SHA1_Final( digest, &ctx );
 
    if( ! hb_parl( 2 ) )
diff --git a/harbour/src/rtl/hbsha1hm.c b/harbour/src/rtl/hbsha1hm.c
index 8b66a62a17..84e9666923 100644
--- a/harbour/src/rtl/hbsha1hm.c
+++ b/harbour/src/rtl/hbsha1hm.c
@@ -60,10 +60,67 @@ HB_FUNC( HB_HMAC_SHA1 )
    HMAC_SHA1_CTX ctx;
 
    HMAC_SHA1_Init( &ctx );
-   HMAC_SHA1_UpdateKey( &ctx, hb_parcx( 2 ), hb_parclen( 2 ) );
+   #if HB_SIZE_MAX > UINT_MAX
+   {
+      const char * buffer = hb_parcx( 2 );
+      HB_SIZE nCount = hb_parclen( 2 );
+      HB_SIZE nDone = 0;
+
+      while( nCount )
+      {
+         unsigned int uiChunk;
+
+         if( nCount > ( HB_SIZE ) UINT_MAX )
+         {
+            uiChunk = UINT_MAX;
+            nCount -= ( HB_SIZE ) uiChunk;
+         }
+         else
+         {
+            uiChunk = ( unsigned int ) nCount;
+            nCount = 0;
+         }
+
+         HMAC_SHA1_UpdateKey( &ctx, buffer + nDone, uiChunk );
+
+         nDone += ( HB_SIZE ) uiChunk;
+      }
+   }
+   #else
+      HMAC_SHA1_UpdateKey( &ctx, hb_parcx( 2 ), hb_parclen( 2 ) );
+   #endif
    HMAC_SHA1_EndKey( &ctx );
+
    HMAC_SHA1_StartMessage( &ctx );
-   HMAC_SHA1_UpdateMessage( &ctx, hb_parcx( 1 ), hb_parclen( 1 ) );
+   #if HB_SIZE_MAX > UINT_MAX
+   {
+      const char * buffer = hb_parcx( 1 );
+      HB_SIZE nCount = hb_parclen( 1 );
+      HB_SIZE nDone = 0;
+
+      while( nCount )
+      {
+         unsigned int uiChunk;
+
+         if( nCount > ( HB_SIZE ) UINT_MAX )
+         {
+            uiChunk = UINT_MAX;
+            nCount -= ( HB_SIZE ) uiChunk;
+         }
+         else
+         {
+            uiChunk = ( unsigned int ) nCount;
+            nCount = 0;
+         }
+
+         HMAC_SHA1_UpdateMessage( &ctx, buffer + nDone, uiChunk );
+
+         nDone += ( HB_SIZE ) uiChunk;
+      }
+   }
+   #else
+      HMAC_SHA1_UpdateMessage( &ctx, hb_parcx( 1 ), hb_parclen( 1 ) );
+   #endif
    HMAC_SHA1_EndMessage( mac, &ctx );
    HMAC_SHA1_Done( &ctx );