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SP int: allow faster NCT exptmod to be compiled in

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For small builds, this may be needed to get the right performance.
This commit is contained in:
Sean Parkinson
2021-02-04 13:02:03 +10:00
parent 250b59f8fd
commit 9792e062c3
1 changed files with 7 additions and 4 deletions
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11
wolfcrypt/src/sp_int.c
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@@ -75,6 +75,8 @@ This library provides single precision (SP) integer math functions.
* WOLFSSL_SP_NONBLOCK Enables "non blocking" mode for SP math, which
* will return FP_WOULDBLOCK for long operations and function must be
* called again until complete.
* WOLFSSL_SP_FAST_NCT_EXPTMOD Enables the faster non-constant time modular
* exponentation implementation.
*/
#if defined(WOLFSSL_SP_MATH) || defined(WOLFSSL_SP_MATH_ALL)
@@ -8851,7 +8853,7 @@ int sp_exptmod(sp_int* b, sp_int* e, sp_int* m, sp_int* r)
* WOLFSSL_HAVE_SP_DH */
#if defined(WOLFSSL_SP_MATH_ALL) || defined(WOLFSSL_HAVE_SP_DH)
#ifndef WOLFSSL_SP_SMALL
#if defined(WOLFSSL_SP_FAST_NCT_EXPTMOD) || !defined(WOLFSSL_SP_SMALL)
/* Internal. Exponentiates b to the power of e modulo m into r: r = b ^ e mod m
* Creates a window of precalculated exponents with base in montgomery form.
* Sliding window and is NOT constant time.
@@ -8880,8 +8882,6 @@ static int _sp_exptmod_nct(sp_int* b, sp_int* e, sp_int* m, sp_int* r)
sp_int* t = NULL;
sp_int* tr = NULL;
sp_int* bm = NULL;
sp_int_digit mp;
sp_int_digit n;
sp_int_digit mask;
bits = sp_count_bits(e);
@@ -8937,6 +8937,9 @@ static int _sp_exptmod_nct(sp_int* b, sp_int* e, sp_int* m, sp_int* r)
}
if ((!done) && (err == MP_OKAY)) {
sp_int_digit mp;
sp_int_digit n;
err = sp_mont_setup(m, &mp);
if (err == MP_OKAY) {
err = sp_mont_norm(&t[0], m);
@@ -12077,7 +12080,7 @@ static int _sp_mont_red(sp_int* a, sp_int* m, sp_int_digit mp)
sp_rshb(a, bits, a);
if (_sp_cmp(a, m) != MP_LT) {
sp_sub(a, m, a);
_sp_sub_off(a, m, a, 0);
}
if (0) {