+#include "system.h"
+
+#include "crypto.h"
+
+#define B64_SIZE(len) ((len) * 4 / 3 + 5)
+
+extern size_t hex2bin(const char *src, void *dst, size_t length);
+extern size_t bin2hex(const void *src, char *dst, size_t length);
+
+// Returns true if string represents a base-10 integer.
+extern bool is_decimal(const char *str);