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SP int: minor improvements to sp_invmod

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This commit is contained in:
Sean Parkinson
2022-01-20 12:47:25 +10:00
parent 30e9d2813e
commit b75fe633ad
1 changed files with 10 additions and 13 deletions
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23
wolfcrypt/src/sp_int.c
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@ -9639,11 +9639,8 @@ int sp_invmod(sp_int* a, sp_int* m, sp_int* r)
sp_int* b = NULL;
sp_int* c = NULL;
sp_int* mm;
int used = ((m == NULL) || (a == NULL)) ? 1 :
((m->used >= a->used) ? m->used + 1 : a->used + 1);
int evenMod = 0;
DECL_SP_INT_ARRAY(t, used, 4);
(void)used;
DECL_SP_INT_ARRAY(t, (m == NULL) ? 1 : (m->used + 1), 4);
if ((a == NULL) || (m == NULL) || (r == NULL) || (r == m)) {
err = MP_VAL;
@ -9655,7 +9652,7 @@ int sp_invmod(sp_int* a, sp_int* m, sp_int* r)
}
#endif
ALLOC_SP_INT_ARRAY(t, (m == NULL) ? 0 : m->used + 1, 4, err, NULL);
ALLOC_SP_INT_ARRAY(t, m->used + 1, 4, err, NULL);
if (err == MP_OKAY) {
u = t[0];
v = t[1];
@ -9721,30 +9718,30 @@ int sp_invmod(sp_int* a, sp_int* m, sp_int* r)
if (sp_iseven(u)) {
sp_div_2(u, u);
if (sp_isodd(b)) {
sp_add(b, mm, b);
_sp_add_off(b, mm, b, 0);
}
sp_div_2(b, b);
}
else if (sp_iseven(v)) {
sp_div_2(v, v);
if (sp_isodd(c)) {
sp_add(c, mm, c);
_sp_add_off(c, mm, c, 0);
}
sp_div_2(c, c);
}
else if (_sp_cmp(u, v) != MP_LT) {
sp_sub(u, v, u);
_sp_sub_off(u, v, u, 0);
if (_sp_cmp(b, c) == MP_LT) {
sp_add(b, mm, b);
_sp_add_off(b, mm, b, 0);
}
sp_sub(b, c, b);
_sp_sub_off(b, c, b, 0);
}
else {
sp_sub(v, u, v);
_sp_sub_off(v, u, v, 0);
if (_sp_cmp(c, b) == MP_LT) {
sp_add(c, mm, c);
_sp_add_off(c, mm, c, 0);
}
sp_sub(c, b, c);
_sp_sub_off(c, b, c, 0);
}
}
if (sp_iszero(u)) {