oxedyne/fe2o3 — fe2o3_crypto/src/c/verify.c

925 bytes, 1 run

created by r1870400018:224, which is this file's identity for as long as the history lasts, whatever it is later renamed to

1	/*-------------------------------------------------
2	This file has been adapted from the implementation
3	(available at https://github.com/pq-crystals/kyber) of
4	"CRYSTALS – Kyber: a CCA-secure module-lattice-based KEM"
5	by : Joppe Bos, Leo Ducas, Eike Kiltz, Tancrede Lepoint,
6	Vadim Lyubashevsky, John M. Schanck, Peter Schwabe & Damien stehle
7	----------------------------------------------------*/
8	#include <string.h>
9	#include <stdint.h>
10	#include "verify.h"
11
12	/* returns 0 for equal strings, 1 for non-equal strings */
13	int verify(const unsigned char a, const unsigned char b, size_t len)
14	{
15	uint64_t r;
16	size_t i;
17	r = 0;
18
19	for (i = 0; i < len; i++)
20	r \|= a[i] ^ b[i];
21
22	r = (-r) >> 63;
23	return r;
24	}
25
26	/* b = 1 means mov, b = 0 means don't mov*/
27	void cmov(unsigned char r, const unsigned char x, size_t len, unsigned char b)
28	{
29	size_t i;
30
31	b = -b;
32	for (i = 0; i < len; i++)
33	r[i] ^= b & (x[i] ^ r[i]);
34	}