Add generic wrappers for performing message digest operations.

src/platform/vboot_reference/tests/signature_digest.c

Index: src/platform/vboot_reference/tests/signature_digest.c
diff --git a/src/platform/vboot_reference/tests/signature_digest.c b/src/platform/vboot_reference/tests/signature_digest.c
index 89d98fe120a415aceb3e72bca1e29c0020044b2d..8dcd8c91e59737e51d42f3480dae4bf30a0109f6 100644
--- a/src/platform/vboot_reference/tests/signature_digest.c
+++ b/src/platform/vboot_reference/tests/signature_digest.c
@@ -17,9 +17,9 @@
 #include <stdlib.h>
 #include <unistd.h>
 
-#include "digest_utility.h"
 #include "padding.h"
 #include "sha.h"
+#include "sha_utility.h"
 
 uint8_t* prepend_digestinfo(int algorithm, uint8_t* digest) {
   const int digest_size = hash_size_map[algorithm];
@@ -52,7 +52,7 @@ int main(int argc, char* argv[]) {
     goto failure;
   }
 
-  if (!(digest = calculate_digest(argv[2], algorithm)))
+  if (!(digest = DigestFile(argv[2], algorithm)))
     goto failure;
 
   info_digest = prepend_digestinfo(algorithm, digest);