* Joel Rees <[email protected]> [2014-10-30 08:38 +0900]: > ----------------------------- > // The core function: test two regions of memory for bytewise equality > with constant time. > // If cmplength is less than min( xlen, ylen ), comparison is incomplete. > static int equals_internal_constime( > const char *x, unsigned int xlen, > const char *y, unsigned int ylen, > int cmplength) { > > int result = 0; > > while ( --cmplength >= 0 ) { > char xtemp = 0; > char ytemp = 0; > > if ( --xlen >= 0 ) xtemp = *x++; > if ( --ylen >= 0 ) ytemp = *y++; > > result |= xtemp ^ ytemp; > } > > return (xlen == ylen) && (result == 0); > } > -----------------------------
Perhaps I am missing the obvious, but 0-1 ist UINT_MAX, which is bigger than zero. And if this would work, the runtime of the loop's body would depend on whether the assignments are executed or not. Nicolas -- To UNSUBSCRIBE, email to [email protected] with a subject of "unsubscribe". Trouble? Contact [email protected] Archive: https://lists.debian.org/[email protected]
