diff --git a/src/file_bac.c b/src/file_bac.c
index b9e01e6c..211d60c2 100644
--- a/src/file_bac.c
+++ b/src/file_bac.c
@@ -34,7 +34,7 @@
 #include "log.h"
 
 /*@
-  @ requires \valid(file_stat);
+  @ requires valid_register_header_check(file_stat);
   @*/
 static void register_header_check_bac(file_stat_t *file_stat);
 
@@ -59,13 +59,9 @@ struct block_header
 
 /*@
   @ requires buffer_size >= 2*0x18;
-  @ requires (buffer_size&1)==0;
-  @ requires \valid_read(buffer+(0..buffer_size-1));
-  @ requires \valid(file_recovery);
   @ requires file_recovery->data_check==&data_check_bac;
-  @ requires file_recovery->calculated_file_size <= PHOTOREC_MAX_FILE_SIZE;
-  @ requires \separated(buffer, file_recovery);
-  @ ensures \result == DC_CONTINUE || \result == DC_STOP;
+  @ requires valid_data_check_param(buffer, buffer_size, file_recovery);
+  @ ensures  valid_data_check_result(\result, file_recovery);
   @ assigns file_recovery->calculated_file_size;
   @*/
 static data_check_t data_check_bac(const unsigned char *buffer, const unsigned int buffer_size, file_recovery_t *file_recovery)
@@ -106,22 +102,16 @@ static data_check_t data_check_bac(const unsigned char *buffer, const unsigned i
 
 /*@
   @ requires buffer_size >= sizeof(struct block_header);
-  @ requires \valid_read(buffer+(0..buffer_size-1));
-  @ requires valid_file_recovery(file_recovery);
-  @ requires \valid(file_recovery_new);
-  @ requires file_recovery_new->blocksize > 0;
   @ requires separation: \separated(&file_hint_bac, buffer, file_recovery, file_recovery_new);
-  @ assigns  *file_recovery_new;
-  @ ensures \result == 0 || \result == 1;
-  @ ensures (\result == 1) ==> (file_recovery_new->file_stat == \null);
-  @ ensures (\result == 1) ==> (file_recovery_new->handle == \null);
+  @ requires valid_header_check_param(buffer, buffer_size, safe_header_only, file_recovery, file_recovery_new);
+  @ ensures  valid_header_check_result(\result, file_recovery_new);
   @ ensures (\result == 1) ==> (file_recovery_new->time == 0);
   @ ensures (\result == 1) ==> (file_recovery_new->file_size == 0);
   @ ensures (\result == 1) ==> (file_recovery_new->calculated_file_size == 0);
   @ ensures (\result == 1) ==> (file_recovery_new->data_check == \null || file_recovery_new->data_check == &data_check_bac);
   @ ensures (\result == 1) ==> (file_recovery_new->file_check == \null || file_recovery_new->file_check == &file_check_size);
   @ ensures (\result == 1) ==> (file_recovery_new->extension == file_hint_bac.extension);
-  @ ensures  \result!=0 ==> valid_file_recovery(file_recovery_new);
+  @ assigns  *file_recovery_new;
   @*/
 static int header_check_bac(const unsigned char *buffer, const unsigned int buffer_size, const unsigned int safe_header_only, const file_recovery_t *file_recovery, file_recovery_t *file_recovery_new)
 {