static void choose_t(ge25519_aff *t, unsigned long long pos, signed char b)
{
/* constant time */
fe25519 v;
*t = ge25519_base_multiples_affine[5*pos+0];
cmov_aff(t, &ge25519_base_multiples_affine[5*pos+1],equal(b,1) | equal(b,-1));
cmov_aff(t, &ge25519_base_multiples_affine[5*pos+2],equal(b,2) | equal(b,-2));
cmov_aff(t, &ge25519_base_multiples_affine[5*pos+3],equal(b,3) | equal(b,-3));
cmov_aff(t, &ge25519_base_multiples_affine[5*pos+4],equal(b,-4));
fe25519_neg(&v, &t->x);
fe25519_cmov(&t->x, &v, negative(b));
}
static void choose_t(ge25519_aff *t, signed char b)
{
fe25519 v;
unsigned char u;
signed char const mask = b >> 7;
u = (b + mask) ^ mask;
*t = ge25519_base_multiples_affine[u];
fe25519_neg(&v, &t->x);
fe25519_cmov(&t->x, &v, negative(b));
}
/* Constant-time version of: if(b) r = p */
static void cmov_aff(ge25519_aff *r, const ge25519_aff *p, unsigned char b)
{
fe25519_cmov(&r->x, &p->x, b);
fe25519_cmov(&r->y, &p->y, b);
}
