lib/jitterentropy/jitterentropy-base.c

128 	uint64_t time = 0;
133 	jent_get_nstime(&time);
139 		time ^= ec->data;
141 	 * We fold the time value as much as possible to ensure that as many
142 	 * bits of the time stamp are included as possible.
145 		shuffle ^= time & mask;
146 		time = time >> bits;
162  * 			      execution time jitter
164  * This function injects the individual bits of the time value into the
171  * the CPU execution time jitter. Any change to the loop in this function
176  * @time time stamp to be injected
185 static uint64_t jent_lfsr_time(struct rand_data *ec, uint64_t time,
205 			uint64_t tmp = time << (DATA_SIZE_BITS - i);
306  * 	1st derivation of the jitter measurement (time delta)
307  * 	2nd derivation of the jitter measurement (delta of time deltas)
308  * 	3rd derivation of the jitter measurement (delta of delta of time deltas)
314  * @current_delta Jitter time delta
335  * This is the heart of the entropy generation: calculate time deltas and
336  * use the CPU jitter in the time deltas. The jitter is injected into the
350 	uint64_t time = 0;
354 	/* Invoke one noise source before time measurement to add variations */
358 	 * Get time stamp and calculate time delta to previous
361 	jent_get_nstime(&time);
362 	current_delta = time - ec->prev_time;
363 	ec->prev_time = time;
373 	 * do) to ensure that every bit position of the input time stamp
376 	 * successive time deltas may have some form of dependency. The
378 	 * time delta value is concatenated with the current time delta.
426 	/* Ensure that the function implements a constant time operation. */
574 	 * time without being moved and an attacker cracks the application,
688 		uint64_t time = 0;
695 		jent_get_nstime(&time);
696 		ec.prev_time = time;
697 		jent_lfsr_time(&ec, time, 0);
701 		if (!time || !time2)
703 		delta = time2 - time;
728 		if (!(time2 > time))
732 		lowdelta = time2 - time;
750 	 * we allow up to three times the time running backwards.
760 	 * Variations of deltas of time must on average be larger
768 	 * Ensure that we have variations in the time stamp below 10 for at least
794 	uint64_t time = 0;
797 	jent_get_nstime(&time);
799 	jent_lfsr_time(ec, time, lfsr_loops_override);
801 	return ((time2 - time));