50 rivejä
1.6 KiB
C
50 rivejä
1.6 KiB
C
#include "verify.h"
|
|
#include <stdint.h>
|
|
#include <string.h>
|
|
|
|
/*************************************************
|
|
* Name: verify
|
|
*
|
|
* Description: Compare two arrays for equality in constant time.
|
|
*
|
|
* Arguments: const unsigned char *a: pointer to first byte array
|
|
* const unsigned char *b: pointer to second byte array
|
|
* size_t len: length of the byte arrays
|
|
*
|
|
* Returns 0 if the byte arrays are equal, 1 otherwise
|
|
**************************************************/
|
|
int PQCLEAN_NEWHOPE1024CPA_CLEAN_verify(const unsigned char *a, const unsigned char *b, size_t len) {
|
|
uint64_t r;
|
|
size_t i;
|
|
r = 0;
|
|
|
|
for (i = 0; i < len; i++) {
|
|
r |= a[i] ^ b[i];
|
|
}
|
|
|
|
r = (-(int64_t)r) >> 63;
|
|
return (int)r;
|
|
}
|
|
|
|
/*************************************************
|
|
* Name: cmov
|
|
*
|
|
* Description: Copy len bytes from x to r if b is 1;
|
|
* don't modify x if b is 0. Requires b to be in {0,1};
|
|
* assumes two's complement representation of negative integers.
|
|
* Runs in constant time.
|
|
*
|
|
* Arguments: unsigned char *r: pointer to output byte array
|
|
* const unsigned char *x: pointer to input byte array
|
|
* size_t len: Amount of bytes to be copied
|
|
* unsigned char b: Condition bit; has to be in {0,1}
|
|
**************************************************/
|
|
void PQCLEAN_NEWHOPE1024CPA_CLEAN_cmov(unsigned char *r, const unsigned char *x, size_t len, unsigned char b) {
|
|
size_t i;
|
|
|
|
b = -b;
|
|
for (i = 0; i < len; i++) {
|
|
r[i] ^= b & (x[i] ^ r[i]);
|
|
}
|
|
}
|