diff --git a/util/cbfstool/common.h b/util/cbfstool/common.h
index 8073d12..86ae484 100644
--- a/util/cbfstool/common.h
+++ b/util/cbfstool/common.h
@@ -210,4 +210,11 @@
 size_t bgets(struct buffer *input, void *output, size_t len);
 size_t bputs(struct buffer *b, const void *data, size_t len);
 
+/* Returns a 0-terminated string containing a hex representation of
+ * len bytes starting at data.
+ * The string is malloc'd and it's the caller's responsibility to free
+ * the memory.
+ * On error, bintohex returns NULL.
+ */
+char *bintohex(uint8_t *data, size_t len);
 #endif