session-android/libaxolotl/jni/ed25519/additions/compare.c
Moxie Marlinspike 2ed8d333d9 Add ed25519
2014-10-20 12:14:18 -07:00

45 lines
663 B
C

#include <string.h>
#include "compare.h"
/* Const-time comparison from SUPERCOP, but here it's only used for
signature verification, so doesn't need to be const-time. But
copied the nacl version anyways. */
int crypto_verify_32_ref(const unsigned char *x, const unsigned char *y)
{
unsigned int differentbits = 0;
#define F(i) differentbits |= x[i] ^ y[i];
F(0)
F(1)
F(2)
F(3)
F(4)
F(5)
F(6)
F(7)
F(8)
F(9)
F(10)
F(11)
F(12)
F(13)
F(14)
F(15)
F(16)
F(17)
F(18)
F(19)
F(20)
F(21)
F(22)
F(23)
F(24)
F(25)
F(26)
F(27)
F(28)
F(29)
F(30)
F(31)
return (1 & ((differentbits - 1) >> 8)) - 1;
}