session-android/libaxolotl/jni/ed25519/additions/compare.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;
}