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Remove function pointers from curve structure

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They're not needed in practice, and removing them decreases the code size
slightly and provides less opportunities for an attacker.
This commit is contained in:
Manuel Pégourié-Gonnard 2019-11-21 09:18:29 +01:00
parent e714332563
commit 1c6f7eae2d
3 changed files with 10 additions and 20 deletions
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16
include/tinycrypt/ecc.h
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@ -131,10 +131,6 @@ struct uECC_Curve_t {
uECC_word_t n[NUM_ECC_WORDS]; uECC_word_t n[NUM_ECC_WORDS];
uECC_word_t G[NUM_ECC_WORDS * 2]; uECC_word_t G[NUM_ECC_WORDS * 2];
uECC_word_t b[NUM_ECC_WORDS]; uECC_word_t b[NUM_ECC_WORDS];
void (*double_jacobian)(uECC_word_t * X1, uECC_word_t * Y1, uECC_word_t * Z1,
uECC_Curve curve);
void (*x_side)(uECC_word_t *result, const uECC_word_t *x, uECC_Curve curve);
void (*mmod_fast)(uECC_word_t *result, uECC_word_t *product);
}; };
/* /*
@ -147,15 +143,6 @@ struct uECC_Curve_t {
void double_jacobian_default(uECC_word_t * X1, uECC_word_t * Y1, void double_jacobian_default(uECC_word_t * X1, uECC_word_t * Y1,
uECC_word_t * Z1, uECC_Curve curve); uECC_word_t * Z1, uECC_Curve curve);
/*
* @brief Computes x^3 + ax + b. result must not overlap x.
* @param result OUT -- x^3 + ax + b
* @param x IN -- value of x
* @param curve IN -- elliptic curve
*/
void x_side_default(uECC_word_t *result, const uECC_word_t *x,
uECC_Curve curve);
/* /*
* @brief Computes result = product % curve_p * @brief Computes result = product % curve_p
* from http://www.nsa.gov/ia/_files/nist-routines.pdf * from http://www.nsa.gov/ia/_files/nist-routines.pdf
@ -201,9 +188,6 @@ static const struct uECC_Curve_t curve_secp256r1 = {
BYTES_TO_WORDS_8(BC, 86, 98, 76, 55, BD, EB, B3), BYTES_TO_WORDS_8(BC, 86, 98, 76, 55, BD, EB, B3),
BYTES_TO_WORDS_8(E7, 93, 3A, AA, D8, 35, C6, 5A) BYTES_TO_WORDS_8(E7, 93, 3A, AA, D8, 35, C6, 5A)
}, },
&double_jacobian_default,
&x_side_default,
&vli_mmod_fast_secp256r1
}; };
uECC_Curve uECC_secp256r1(void); uECC_Curve uECC_secp256r1(void);

12
tinycrypt/ecc.c
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@ -622,7 +622,13 @@ void double_jacobian_default(uECC_word_t * X1, uECC_word_t * Y1,
uECC_vli_set(Y1, t4); uECC_vli_set(Y1, t4);
} }
void x_side_default(uECC_word_t *result, /*
* @brief Computes x^3 + ax + b. result must not overlap x.
* @param result OUT -- x^3 + ax + b
* @param x IN -- value of x
* @param curve IN -- elliptic curve
*/
static void x_side_default(uECC_word_t *result,
const uECC_word_t *x, const uECC_word_t *x,
uECC_Curve curve) uECC_Curve curve)
{ {
@ -775,7 +781,7 @@ static void XYcZ_initial_double(uECC_word_t * X1, uECC_word_t * Y1,
uECC_vli_set(Y2, Y1); uECC_vli_set(Y2, Y1);
apply_z(X1, Y1, z); apply_z(X1, Y1, z);
curve->double_jacobian(X1, Y1, z, curve); double_jacobian_default(X1, Y1, z, curve);
apply_z(X2, Y2, z); apply_z(X2, Y2, z);
} }
@ -1050,7 +1056,7 @@ int uECC_valid_point(const uECC_word_t *point, uECC_Curve curve)
} }
uECC_vli_modMult_fast(tmp1, point + num_words, point + num_words); uECC_vli_modMult_fast(tmp1, point + num_words, point + num_words);
curve->x_side(tmp2, point, curve); /* tmp2 = x^3 + ax + b */ x_side_default(tmp2, point, curve); /* tmp2 = x^3 + ax + b */
/* Make sure that y^2 == x^3 + ax + b */ /* Make sure that y^2 == x^3 + ax + b */
if (uECC_vli_equal(tmp1, tmp2) != 0) if (uECC_vli_equal(tmp1, tmp2) != 0)

2
tinycrypt/ecc_dsa.c
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@ -280,7 +280,7 @@ int uECC_verify(const uint8_t *public_key, const uint8_t *message_hash,
for (i = num_bits - 2; i >= 0; --i) { for (i = num_bits - 2; i >= 0; --i) {
uECC_word_t index; uECC_word_t index;
curve->double_jacobian(rx, ry, z, curve); double_jacobian_default(rx, ry, z, curve);
index = (!!uECC_vli_testBit(u1, i)) | ((!!uECC_vli_testBit(u2, i)) << 1); index = (!!uECC_vli_testBit(u1, i)) | ((!!uECC_vli_testBit(u2, i)) << 1);
point = points[index]; point = points[index];