*With DVDCSS_METHOD=disc or key, the keys are no longer buffered on start.
The title key is still read at each block but it is checked for change
before decryption.

extras/libdvdcss/css.c

@@ -2,7 +2,7 @@
  * css.c: Functions for DVD authentification and unscrambling
  *****************************************************************************
  * Copyright (C) 1999-2001 VideoLAN
- * $Id: css.c,v 1.19 2002/01/04 14:01:34 sam Exp $
+ * $Id: css.c,v 1.20 2002/01/14 22:06:57 stef Exp $
  *
  * Author: Stphane Borel <stef@via.ecp.fr>
  *         Hkan Hjort <d95hjort@dtek.chalmers.se>
@@ -475,16 +475,22 @@ int CSSGetTitleKey( dvdcss_handle dvdcss, int i_pos )
             _dvdcss_error( dvdcss, "ioctl_ReadTitleKey failed" );
             return -1;
         }
-        /* Unencrypt title key using bus key */
-        for( i = 0 ; i < KEY_SIZE ; i++ )
+
+        if( memcmp( p_key, dvdcss->css.p_unenc_key, KEY_SIZE ) )
         {
-            p_key[ i ] ^= dvdcss->css.disc.p_key_check[ 4 - (i % KEY_SIZE) ];
-        }
+            memcpy( dvdcss->css.p_unenc_key, p_key, KEY_SIZE );
+            
+            /* Unencrypt title key using bus key */
+            for( i = 0 ; i < KEY_SIZE ; i++ )
+            {
+                p_key[ i ] ^= dvdcss->css.disc.p_key_check[ 4 - (i % KEY_SIZE ) ];
+            }
 
-        /* Title key decryption needs one inversion 0xff */
-        CSSDecryptKey( p_key, dvdcss->css.disc.p_disc_key, 0xff );
+            /* Title key decryption needs one inversion 0xff */
+            CSSDecryptKey( p_key, dvdcss->css.disc.p_disc_key, 0xff );
 
-        memcpy( dvdcss->css.p_title_key, p_key, sizeof(dvd_key_t) );
+            memcpy( dvdcss->css.p_title_key, p_key, KEY_SIZE );
+        }
 
         return 0;
     } // (dvdcss->i_method == DVDCSS_METHOD_TITLE) || (dvdcss->b_ioctls == 0)

extras/libdvdcss/css.h

@@ -2,7 +2,7 @@
  * css.h: Structures for DVD authentification and unscrambling
  *****************************************************************************
  * Copyright (C) 1999-2001 VideoLAN
- * $Id: css.h,v 1.6 2001/10/13 15:34:21 stef Exp $
+ * $Id: css.h,v 1.7 2002/01/14 22:06:57 stef Exp $
  *
  * Author: Stphane Borel <stef@via.ecp.fr>
  *
@@ -51,7 +51,8 @@ typedef struct css_s
 {
     int             i_agid;
     disc_t          disc;
-    dvd_key_t       p_title_key;
+    dvd_key_t       p_unenc_key; /* title key before decryption */
+    dvd_key_t       p_title_key; /* title key after decryption */
 } css_t;
 
 /*****************************************************************************

extras/libdvdcss/libdvdcss.c

@@ -2,7 +2,7 @@
  * libdvdcss.c: DVD reading library.
  *****************************************************************************
  * Copyright (C) 1998-2001 VideoLAN
- * $Id: libdvdcss.c,v 1.26 2001/12/30 07:09:54 sam Exp $
+ * $Id: libdvdcss.c,v 1.27 2002/01/14 22:06:57 stef Exp $
  *
  * Authors: Stphane Borel <stef@via.ecp.fr>
  *          Samuel Hocevar <sam@zoy.org>
@@ -184,6 +184,8 @@ extern dvdcss_handle dvdcss_open ( char *psz_target )
         }
     }
 
+    memset( dvdcss->css.p_unenc_key, 0, KEY_SIZE );
+
 #ifndef WIN32
     if( psz_raw_device != NULL )
     {
@@ -209,8 +211,25 @@ extern int dvdcss_seek ( dvdcss_handle dvdcss, int i_blocks, int i_flags )
 {
     /* title cracking method is too slow to be used at each seek */
     if( ( ( i_flags & DVDCSS_SEEK_MPEG )
-             && ( dvdcss->i_method != DVDCSS_METHOD_TITLE ) ) 
-       || ( i_flags & DVDCSS_SEEK_KEY ) )
+             && ( dvdcss->i_method != DVDCSS_METHOD_TITLE ) ) )
+    {
+        int     i_ret;
+
+        /* Crack or decrypt CSS title key for current VTS */
+        i_ret = CSSGetTitleKey( dvdcss, i_blocks );
+
+        if( i_ret < 0 )
+        {
+            _dvdcss_error( dvdcss, "fatal error in vts css key" );
+            return i_ret;
+        }
+        else if( i_ret > 0 )
+        {
+            _dvdcss_error( dvdcss, "decryption unavailable" );
+            return -1;
+        }
+    }
+    else if( i_flags & DVDCSS_SEEK_KEY )
     {
         /* check the title key */
         if( dvdcss_title( dvdcss, i_blocks ) )