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ECC, DH: improve encrypted memory implementations

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This commit is contained in:
Sean Parkinson
2022-06-06 08:40:09 +10:00
parent c83120d8c8
commit 0bcd38f7d8
2 changed files with 35 additions and 0 deletions
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16
wolfcrypt/src/ecc.c
View File

@ -2788,26 +2788,33 @@ static int wc_ecc_gen_z(WC_RNG* rng, int size, ecc_point* p,
err = mp_init(mu);
if (err == MP_OKAY)
err = mp_montgomery_calc_normalization(mu, modulus);
/* Generate random value to multiply into p->z. */
if (err == MP_OKAY)
err = wc_ecc_gen_k(rng, size, ty, modulus);
/* Convert to montogmery form. */
if (err == MP_OKAY)
err = mp_mulmod(ty, mu, modulus, ty);
/* Multiply random value into p->z. */
if (err == MP_OKAY)
err = mp_mul(p->z, ty, p->z);
if (err == MP_OKAY)
err = mp_montgomery_reduce(p->z, modulus, mp);
/* Square random value for X (X' = X / Z^2). */
if (err == MP_OKAY)
err = mp_sqr(ty, tx);
if (err == MP_OKAY)
err = mp_montgomery_reduce(tx, modulus, mp);
/* Multiply square of random by random value for Y. */
if (err == MP_OKAY)
err = mp_mul(ty, tx, ty);
if (err == MP_OKAY)
err = mp_montgomery_reduce(ty, modulus, mp);
/* Multiply square into X. */
if (err == MP_OKAY)
err = mp_mul(p->x, tx, p->x);
if (err == MP_OKAY)
err = mp_montgomery_reduce(p->x, modulus, mp);
/* Multiply cube into Y (Y' = Y / Z^3). */
if (err == MP_OKAY)
err = mp_mul(p->y, ty, p->y);
if (err == MP_OKAY)
@ -3108,12 +3115,21 @@ static int ecc_mulmod(const mp_int* k, ecc_point* P, ecc_point* Q,
/* Ensure 'swap' changes to a previously unseen value. */
swap += (kt->dp[j] >> cnt) + swap;
/* R[0] = 2*R[0] */
err = ecc_projective_dbl_point_safe(R[set + 0], R[set + 0], a, modulus,
mp);
if (err == MP_OKAY) {
/* R[0] = R[1] + R[0] */
err = ecc_projective_add_point_safe(R[set + 0], R[set + 1],
R[set + 0], a, modulus, mp, &infinity);
}
/* R[1]->z * 2 - same point. */
mp_addmod_ct(R[set + 1]->z, R[set + 1]->z, modulus, R[set + 1]->z);
mp_addmod_ct(R[set + 1]->x, R[set + 1]->x, modulus, R[set + 1]->x);
mp_addmod_ct(R[set + 1]->x, R[set + 1]->x, modulus, R[set + 1]->x);
mp_addmod_ct(R[set + 1]->y, R[set + 1]->y, modulus, R[set + 1]->y);
mp_addmod_ct(R[set + 1]->y, R[set + 1]->y, modulus, R[set + 1]->y);
mp_addmod_ct(R[set + 1]->y, R[set + 1]->y, modulus, R[set + 1]->y);
}
/* Step 4: end for */
/* Swap back if last bit is 0. */

19
wolfcrypt/src/tfm.c
View File

@ -2423,12 +2423,16 @@ static int _fp_exptmod_nct(fp_int * G, fp_int * X, fp_int * P, fp_int * Y)
#ifdef TFM_TIMING_RESISTANT
#if DIGIT_BIT <= 16
#define WINSIZE 2
#define WINMASK 0x3
#elif DIGIT_BIT <= 32
#define WINSIZE 3
#define WINMASK 0x7
#elif DIGIT_BIT <= 64
#define WINSIZE 4
#define WINMASK 0xf
#elif DIGIT_BIT <= 128
#define WINSIZE 5
#define WINMASK 0x1f
#endif
/* y = 2**x (mod b)
@ -2544,7 +2548,12 @@ static int _fp_exptmod_base_2(fp_int * X, int digits, fp_int * P,
y = (int)(buf >> (DIGIT_BIT - 1)) & 1;
buf <<= (fp_digit)1;
/* add bit to the window */
#ifndef WC_PROTECT_ENCRYPTED_MEM
bitbuf |= (y << (WINSIZE - ++bitcpy));
#else
/* Ensure value changes even when y is zero. */
bitbuf += (WINMASK + 1) + (y << (WINSIZE - ++bitcpy));
#endif
if (bitcpy == WINSIZE) {
/* ok window is filled so square as required and multiply */
@ -2567,7 +2576,12 @@ static int _fp_exptmod_base_2(fp_int * X, int digits, fp_int * P,
}
/* then multiply by 2^bitbuf */
#ifndef WC_PROTECT_ENCRYPTED_MEM
err = fp_mul_2d(res, bitbuf, res);
#else
/* Get the window bits. */
err = fp_mul_2d(res, bitbuf & WINMASK, res);
#endif
if (err != FP_OKAY) {
#ifdef WOLFSSL_SMALL_STACK
XFREE(res, NULL, DYNAMIC_TYPE_TMP_BUFFER);
@ -2592,7 +2606,12 @@ static int _fp_exptmod_base_2(fp_int * X, int digits, fp_int * P,
/* empty window and reset */
bitcpy = 0;
#ifndef WC_PROTECT_ENCRYPTED_MEM
bitbuf = 0;
#else
/* Ensure value is new even when bottom bits are 0. */
bitbuf = (WINMASK + 1) + (bitbuf & ~WINMASK);
#endif
}
}