+/*!
+ @function mbr_sid_to_string
+ @abstract convert a SID to a corresponding character string representation
+ @discussion for use in situations where an external representation of a SID is required.
+ @param sid is the SID to be converted
+ @param string is a buffer that will be filled in with a nul-terminated string
+ representation of the SID. The buffer must be at least 194 characters in length.
+ @result returns 0 on success or appropriate errno code.
+ */
+int mbr_sid_to_string(const nt_sid_t *sid, char *string);
+
+/*!
+ @function mbr_string_to_sid
+ @abstract convert a character string representation of a sid to an nt_sid_t value
+ @discussion for converting an external representation of a sid.
+ @param string is a buffer containing a nul-terminated string representation of a SID
+ @param sid is the target of the conversion
+ @result returns 0 on success or appropriate errno code.
+ */
+int mbr_string_to_sid(const char *string, nt_sid_t *sid);
+