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tomcrypt/ecc.c
Tom St Denis 5581d44fd4 added libtomcrypt-0.77
2010-06-16 12:37:50 +02:00

837 lines
23 KiB
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/* Implements ECC over Z/pZ for curve y^2 = x^3 - 3x + b
*
* All curves taken from NIST recommendation paper of July 1999
* Available at http://csrc.nist.gov/cryptval/dss.htm
*/
#include "mycrypt.h"
#ifdef MECC
/* This holds the key settings. ***MUST*** be organized by size from smallest to largest. */
static const struct {
int size;
char *name, *prime, *B, *order, *Gx, *Gy;
} sets[] = {
#ifdef ECC160
{
20,
"ECC-160",
/* prime */
"1461501637330902918203684832716283019655932542983",
/* B */
"1C9E7C2E5891CBE097BD46",
/* order */
"1461501637330902918203686297565868358251373258181",
/* Gx */
"2DCF462904B478D868A7FF3F2BF1FCD9",
/* Gy */
"DFFAF2EE3848FA75FB967CEC7B9A399E085ACED8",
},
#endif
#ifdef ECC192
{
24,
"ECC-192",
/* prime */
"6277101735386680763835789423207666416083908700390324961279",
/* B */
"64210519e59c80e70fa7e9ab72243049feb8deecc146b9b1",
/* order */
"6277101735386680763835789423176059013767194773182842284081",
/* Gx */
"188da80eb03090f67cbf20eb43a18800f4ff0afd82ff1012",
/* Gy */
"07192b95ffc8da78631011ed6b24cdd573f977a11e794811"
},
#endif
#ifdef ECC224
{
28,
"ECC-224",
/* prime */
"26959946667150639794667015087019630673637144422540572481103610249951",
/* B */
"2051BA041508CED34B3",
/* order */
"26959946667150639794667015087019637467111563745054605861463538557247",
/* Gx */
"2DCF462904B478D868A7FF3F2BF1FCD9",
/* Gy */
"CF337F320BC44A15C3EDB8C4258BB958E57A0CAFA73EB46E9C4BA9AE",
},
#endif
#ifdef ECC256
{
32,
"ECC-256",
/* Prime */
"115792089210356248762697446949407573530086143415290314195533631308867097853951",
/* B */
"5ac635d8aa3a93e7b3ebbd55769886bc651d06b0cc53b0f63bce3c3e27d2604b",
/* Order */
"115792089210356248762697446949407573529996955224135760342422259061068512044369",
/* Gx */
"6b17d1f2e12c4247f8bce6e563a440f277037d812deb33a0f4a13945d898c296",
/* Gy */
"4fe342e2fe1a7f9b8ee7eb4a7c0f9e162bce33576b315ececbb6406837bf51f5"
},
#endif
#ifdef ECC384
{
48,
"ECC-384",
/* prime */
"394020061963944792122790401001436138050797392704654466679482934042457217714968"
"70329047266088258938001861606973112319",
/* B */
"b3312fa7e23ee7e4988e056be3f82d19181d9c6efe8141120314088f5013875ac656398d8a2ed1"
"9d2a85c8edd3ec2aef",
/* Order */
"394020061963944792122790401001436138050797392704654466679469052796276593991132"
"63569398956308152294913554433653942643",
/* Gx and Gy */
"aa87ca22be8b05378eb1c71ef320ad746e1d3b628ba79b9859f741e082542a385502f25dbf5529"
"6c3a545e3872760ab7",
"3617de4a96262c6f5d9e98bf9292dc29f8f41dbd289a147ce9da3113b5f0b8c00a60b1ce1d7e81"
"9d7a431d7c90ea0e5f"
},
#endif
#ifdef ECC521
{
65,
"ECC-521",
/* prime */
"686479766013060971498190079908139321726943530014330540939446345918554318339765"
"6052122559640661454554977296311391480858037121987999716643812574028291115057151",
/* B */
"051953eb9618e1c9a1f929a21a0b68540eea2da725b99b315f3b8b489918ef109e156193951ec7"
"e937b1652c0bd3bb1bf073573df883d2c34f1ef451fd46b503f00",
/* Order */
"686479766013060971498190079908139321726943530014330540939446345918554318339765"
"5394245057746333217197532963996371363321113864768612440380340372808892707005449",
/* Gx and Gy */
"c6858e06b70404e9cd9e3ecb662395b4429c648139053fb521f828af606b4d3dbaa14b5e77efe7"
"5928fe1dc127a2ffa8de3348b3c1856a429bf97e7e31c2e5bd66",
"11839296a789a3bc0045c8a5fb42c7d1bd998f54449579b446817afbd17273e662c97ee72995ef"
"42640c550b9013fad0761353c7086a272c24088be94769fd16650",
},
#endif
{
0,
NULL, NULL, NULL, NULL, NULL, NULL
}
};
#if 0
/* you plug in a prime and B value and it finds a pseudo-random base point */
void ecc_find_base(void)
{
static char *prime = "26959946667150639794667015087019630673637144422540572481103610249951";
static char *order = "26959946667150639794667015087019637467111563745054605861463538557247";
static char *b = "9538957348957353489587";
mp_int pp, p, r, B, tmp1, tmp2, tx, ty, x, y;
char buf[4096];
int i;
mp_init_multi(&tx, &ty, &x, &y, &p, &pp, &r, &B, &tmp1, &tmp2, NULL);
mp_read_radix(&p, prime, 10);
mp_read_radix(&r, order, 10);
mp_read_radix(&B, b, 10);
/* get (p+1)/4 */
mp_add_d(&p, 1, &pp);
mp_div_2(&pp, &pp);
mp_div_2(&pp, &pp);
buf[0] = 0;
do {
printf("."); fflush(stdout);
/* make a random value of x */
for (i = 0; i < 16; i++) buf[i+1] = rand() & 255;
mp_read_raw(&x, buf, 17);
mp_copy(&x, &tx);
/* now compute x^3 - 3x + b */
mp_expt_d(&x, 3, &tmp1);
mp_mul_d(&x, 3, &tmp2);
mp_sub(&tmp1, &tmp2, &tmp1);
mp_add(&tmp1, &B, &tmp1);
mp_mod(&tmp1, &p, &tmp1);
/* now compute sqrt via x^((p+1)/4) */
mp_exptmod(&tmp1, &pp, &p, &tmp2);
mp_copy(&tmp2, &ty);
/* now square it */
mp_sqrmod(&tmp2, &p, &tmp2);
/* tmp2 should equal tmp1 */
} while (mp_cmp(&tmp1, &tmp2));
/* now output values in way that libtomcrypt wants */
mp_todecimal(&p, buf);
printf("\n\np==%s\n", buf);
mp_tohex(&B, buf);
printf("b==%s\n", buf);
mp_todecimal(&r, buf);
printf("r==%s\n", buf);
mp_tohex(&tx, buf);
printf("Gx==%s\n", buf);
mp_tohex(&ty, buf);
printf("Gy==%s\n", buf);
mp_clear_multi(&tx, &ty, &x, &y, &p, &pp, &r, &B, &tmp1, &tmp2, NULL);
}
#endif
static int is_valid_idx(int n)
{
int x;
for (x = 0; sets[x].size; x++);
if ((n < 0) || (n >= x)) {
return 0;
}
return 1;
}
static ecc_point *new_point(void)
{
ecc_point *p;
p = XMALLOC(sizeof(ecc_point));
if (p == NULL) {
return NULL;
}
if (mp_init_multi(&p->x, &p->y, NULL) != MP_OKAY) {
XFREE(p);
return NULL;
}
return p;
}
static void del_point(ecc_point *p)
{
mp_clear_multi(&p->x, &p->y, NULL);
XFREE(p);
}
/* double a point R = 2P, R can be P*/
static int dbl_point(ecc_point *P, ecc_point *R, mp_int *modulus)
{
mp_int s, tmp, tmpx;
int res;
if (mp_init_multi(&s, &tmp, &tmpx, NULL) != MP_OKAY) {
return CRYPT_MEM;
}
/* s = (3Xp^2 + a) / (2Yp) */
if (mp_mul_2(&P->y, &tmp) != MP_OKAY) { goto error; } /* tmp = 2*y */
if (mp_invmod(&tmp, modulus, &tmp) != MP_OKAY) { goto error; } /* tmp = 1/tmp mod modulus */
if (mp_sqr(&P->x, &s) != MP_OKAY) { goto error; } /* s = x^2 */
if (mp_mul_d(&s,(mp_digit)3, &s) != MP_OKAY) { goto error; } /* s = 3*(x^2) */
if (mp_sub_d(&s,(mp_digit)3, &s) != MP_OKAY) { goto error; } /* s = 3*(x^2) - 3 */
if (mp_mulmod(&s, &tmp, modulus, &s) != MP_OKAY) { goto error; } /* s = tmp * s mod modulus */
/* Xr = s^2 - 2Xp */
if (mp_sqr(&s, &tmpx) != MP_OKAY) { goto error; } /* tmpx = s^2 */
if (mp_sub(&tmpx, &P->x, &tmpx) != MP_OKAY) { goto error; } /* tmpx = tmpx - x */
if (mp_submod(&tmpx, &P->x, modulus, &tmpx) != MP_OKAY) { goto error; } /* tmpx = tmpx - x mod modulus */
/* Yr = -Yp + s(Xp - Xr) */
if (mp_sub(&P->x, &tmpx, &tmp) != MP_OKAY) { goto error; } /* tmp = x - tmpx */
if (mp_mul(&tmp, &s, &tmp) != MP_OKAY) { goto error; } /* tmp = tmp * s */
if (mp_submod(&tmp, &P->y, modulus, &R->y) != MP_OKAY) { goto error; } /* y = tmp - y mod modulus */
if (mp_copy(&tmpx, &R->x) != MP_OKAY) { goto error; } /* x = tmpx */
res = CRYPT_OK;
goto done;
error:
res = CRYPT_MEM;
done:
mp_clear_multi(&tmpx, &tmp, &s, NULL);
return res;
}
/* add two different points over Z/pZ, R = P + Q, note R can equal either P or Q */
static int add_point(ecc_point *P, ecc_point *Q, ecc_point *R, mp_int *modulus)
{
mp_int s, tmp, tmpx;
int res;
if (mp_init(&tmp) != MP_OKAY) {
return CRYPT_MEM;
}
/* is P==Q or P==-Q? */
mp_neg(&Q->y, &tmp);
mp_mod(&tmp, modulus, &tmp);
if (!mp_cmp(&P->x, &Q->x))
if (!mp_cmp(&P->y, &Q->y) || !mp_cmp(&P->y, &tmp)) {
mp_clear(&tmp);
return dbl_point(P, R, modulus);
}
if (mp_init_multi(&tmpx, &s, NULL) != MP_OKAY) {
mp_clear(&tmp);
return CRYPT_MEM;
}
/* get s = (Yp - Yq)/(Xp-Xq) mod p */
if (mp_submod(&P->x, &Q->x, modulus, &tmp) != MP_OKAY) { goto error; } /* tmp = Px - Qx mod modulus */
if (mp_invmod(&tmp, modulus, &tmp) != MP_OKAY) { goto error; } /* tmp = 1/tmp mod modulus */
if (mp_sub(&P->y, &Q->y, &s) != MP_OKAY) { goto error; } /* s = Py - Qy mod modulus */
if (mp_mulmod(&s, &tmp, modulus, &s) != MP_OKAY) { goto error; } /* s = s * tmp mod modulus */
/* Xr = s^2 - Xp - Xq */
if (mp_sqrmod(&s, modulus, &tmp) != MP_OKAY) { goto error; } /* tmp = s^2 mod modulus */
if (mp_sub(&tmp, &P->x, &tmp) != MP_OKAY) { goto error; } /* tmp = tmp - Px */
if (mp_sub(&tmp, &Q->x, &tmpx) != MP_OKAY) { goto error; } /* tmpx = tmp - Qx */
/* Yr = -Yp + s(Xp - Xr) */
if (mp_sub(&P->x, &tmpx, &tmp) != MP_OKAY) { goto error; } /* tmp = Px - tmpx */
if (mp_mul(&tmp, &s, &tmp) != MP_OKAY) { goto error; } /* tmp = tmp * s */
if (mp_submod(&tmp, &P->y, modulus, &R->y) != MP_OKAY) { goto error; } /* Ry = tmp - Py mod modulus */
if (mp_mod(&tmpx, modulus, &R->x) != MP_OKAY) { goto error; } /* Rx = tmpx mod modulus */
res = CRYPT_OK;
goto done;
error:
res = CRYPT_MEM;
done:
mp_clear_multi(&s, &tmpx, &tmp, NULL);
return res;
}
/* perform R = kG where k == integer and G == ecc_point */
static int ecc_mulmod(mp_int *k, ecc_point *G, ecc_point *R, mp_int *modulus, int idx)
{
ecc_point *tG;
int i, j, z, first, res;
mp_digit d;
unsigned char bits[768];
/* get bits of k */
for (z = i = 0; z < (int)USED(k); z++) {
d = DIGIT(k, z);
#define DO1 bits[i++] = d&1; d >>= 1;
#define DO2 DO1 DO1
#define DO4 DO2 DO2
DO4; DO4; DO4; DO4
#undef DO4
#undef DO2
#undef DO1
}
/* make a copy of G incase R==G */
tG = new_point();
if (tG == NULL) {
return CRYPT_MEM;
}
/* tG = G */
if (mp_copy(&G->x, &tG->x) != MP_OKAY) { goto error; }
if (mp_copy(&G->y, &tG->y) != MP_OKAY) { goto error; }
/* set result to G, R = G */
if (mp_copy(&G->x, &R->x) != MP_OKAY) { goto error; }
if (mp_copy(&G->y, &R->y) != MP_OKAY) { goto error; }
first = 0;
/* now do dbl+add through all the bits */
for (j = i-1; j >= 0; j--) {
if (first) {
if (dbl_point(R, R, modulus) != CRYPT_OK) { goto error; }
}
if (bits[j] == 1) {
if (first) {
if (add_point(R, tG, R, modulus) != CRYPT_OK) { goto error; }
}
first = 1;
}
}
res = CRYPT_OK;
goto done;
error:
res = CRYPT_MEM;
done:
del_point(tG);
#ifdef CLEAN_STACK
zeromem(bits, sizeof(bits));
#endif
return res;
}
int ecc_test(void)
{
mp_int modulus, order;
ecc_point *G, *GG;
int i, res, primality;
if (mp_init_multi(&modulus, &order, NULL) != MP_OKAY) {
return CRYPT_MEM;
}
G = new_point();
if (G == NULL) {
mp_clear_multi(&modulus, &order, NULL);
return CRYPT_MEM;
}
GG = new_point();
if (GG == NULL) {
mp_clear_multi(&modulus, &order, NULL);
del_point(G);
return CRYPT_MEM;
}
for (i = 0; sets[i].size; i++) {
if (mp_read_radix(&modulus, (unsigned char *)sets[i].prime, 10) != MP_OKAY) { goto error; }
if (mp_read_radix(&order, (unsigned char *)sets[i].order, 10) != MP_OKAY) { goto error; }
/* is prime actually prime? */
if (is_prime(&modulus, &primality) != CRYPT_OK) { goto error; }
if (primality == 0) {
res = CRYPT_FAIL_TESTVECTOR;
goto done1;
}
/* is order prime ? */
if (is_prime(&order, &primality) != CRYPT_OK) { goto error; }
if (primality == 0) {
res = CRYPT_FAIL_TESTVECTOR;
goto done1;
}
if (mp_read_radix(&G->x, (unsigned char *)sets[i].Gx, 16) != MP_OKAY) { goto error; }
if (mp_read_radix(&G->y, (unsigned char *)sets[i].Gy, 16) != MP_OKAY) { goto error; }
/* then we should have G == (order + 1)G */
if (mp_add_d(&order, 1, &order) != MP_OKAY) { goto error; }
if (ecc_mulmod(&order, G, GG, &modulus, i) != CRYPT_OK) { goto error; }
if (mp_cmp(&G->x, &GG->x) || mp_cmp(&G->y, &GG->y)) {
res = CRYPT_FAIL_TESTVECTOR;
goto done1;
}
}
res = CRYPT_OK;
goto done1;
error:
res = CRYPT_MEM;
done1:
del_point(GG);
del_point(G);
mp_clear_multi(&order, &modulus, NULL);
return res;
}
void ecc_sizes(int *low, int *high)
{
int i;
_ARGCHK(low != NULL);
_ARGCHK(high != NULL);
*low = INT_MAX;
*high = 0;
for (i = 0; sets[i].size; i++) {
if (sets[i].size < *low) {
*low = sets[i].size;
}
if (sets[i].size > *high) {
*high = sets[i].size;
}
}
}
int ecc_make_key(prng_state *prng, int wprng, int keysize, ecc_key *key)
{
int x, res, errno;
ecc_point *base;
mp_int prime;
unsigned char buf[4096];
_ARGCHK(key != NULL);
/* good prng? */
if ((errno = prng_is_valid(wprng)) != CRYPT_OK) {
return errno;
}
/* find key size */
for (x = 0; (keysize > sets[x].size) && (sets[x].size); x++);
keysize = sets[x].size;
if (sets[x].size == 0) {
return CRYPT_INVALID_KEYSIZE;
}
key->idx = x;
/* make up random string */
buf[0] = 0;
if (prng_descriptor[wprng].read(buf+1, keysize, prng) != (unsigned long)keysize) {
return CRYPT_ERROR_READPRNG;
}
/* setup the key variables */
if (mp_init_multi(&key->pubkey.x, &key->pubkey.y, &key->k, &prime, NULL) != MP_OKAY) {
return CRYPT_MEM;
}
base = new_point();
if (base == NULL) {
mp_clear_multi(&key->pubkey.x, &key->pubkey.y, &key->k, &prime, NULL);
return CRYPT_MEM;
}
/* read in the specs for this key */
if (mp_read_radix(&prime, (unsigned char *)sets[x].prime, 10) != MP_OKAY) { goto error; }
if (mp_read_radix(&base->x, (unsigned char *)sets[x].Gx, 16) != MP_OKAY) { goto error; }
if (mp_read_radix(&base->y, (unsigned char *)sets[x].Gy, 16) != MP_OKAY) { goto error; }
if (mp_read_raw(&key->k, (unsigned char *)buf, keysize+1) != MP_OKAY) { goto error; }
/* make the public key */
if (ecc_mulmod(&key->k, base, &key->pubkey, &prime, x) != CRYPT_OK) { goto error; }
key->type = PK_PRIVATE;
/* free up ram */
res = CRYPT_OK;
goto done;
error:
res = CRYPT_MEM;
done:
del_point(base);
mp_clear(&prime);
#ifdef CLEAN_STACK
zeromem(buf, sizeof(buf));
#endif
return res;
}
void ecc_free(ecc_key *key)
{
_ARGCHK(key != NULL);
mp_clear_multi(&key->pubkey.x, &key->pubkey.y, &key->k, NULL);
}
static int compress_y_point(ecc_point *pt, int idx, int *result)
{
mp_int tmp, tmp2, p;
int res;
_ARGCHK(pt != NULL);
_ARGCHK(result != NULL);
if (mp_init_multi(&tmp, &tmp2, &p, NULL) != MP_OKAY) {
return CRYPT_MEM;
}
/* get x^3 - 3x + b */
if (mp_read_radix(&p, (unsigned char *)sets[idx].B, 16) != MP_OKAY) { goto error; } /* p = B */
if (mp_expt_d(&pt->x, 3, &tmp) != MP_OKAY) { goto error; } /* tmp = pX^3 */
if (mp_mul_d(&pt->x, 3, &tmp2) != MP_OKAY) { goto error; } /* tmp2 = 3*pX^3 */
if (mp_sub(&tmp, &tmp2, &tmp) != MP_OKAY) { goto error; } /* tmp = tmp - tmp2 */
if (mp_add(&tmp, &p, &tmp) != MP_OKAY) { goto error; } /* tmp = tmp + p */
if (mp_read_radix(&p, (unsigned char *)sets[idx].prime, 10) != MP_OKAY) { goto error; } /* p = prime */
if (mp_mod(&tmp, &p, &tmp) != MP_OKAY) { goto error; } /* tmp = tmp mod p */
/* now find square root */
if (mp_add_d(&p, 1, &tmp2) != MP_OKAY) { goto error; } /* tmp2 = p + 1 */
if (mp_div_2(&tmp2, &tmp2) != MP_OKAY) { goto error; } /* tmp2 = tmp2/2 */
if (mp_div_2(&tmp2, &tmp2) != MP_OKAY) { goto error; } /* tmp2 = (p+1)/4 */
if (mp_exptmod(&tmp, &tmp2, &p, &tmp) != MP_OKAY) { goto error; } /* tmp = (x^3 - 3x + b)^((p+1)/4) mod p */
/* if tmp equals the y point give a 0, otherwise 1 */
if (mp_cmp(&tmp, &pt->y) == 0) {
*result = 0;
} else {
*result = 1;
}
res = CRYPT_OK;
goto done;
error:
res = CRYPT_MEM;
done:
mp_clear_multi(&p, &tmp, &tmp2, NULL);
return res;
}
static int expand_y_point(ecc_point *pt, int idx, int result)
{
mp_int tmp, tmp2, p;
int res;
_ARGCHK(pt != NULL);
if (mp_init_multi(&tmp, &tmp2, &p, NULL) != MP_OKAY) {
return CRYPT_MEM;
}
/* get x^3 - 3x + b */
if (mp_read_radix(&p, (unsigned char *)sets[idx].B, 16) != MP_OKAY) { goto error; } /* p = B */
if (mp_expt_d(&pt->x, 3, &tmp) != MP_OKAY) { goto error; } /* tmp = pX^3 */
if (mp_mul_d(&pt->x, 3, &tmp2) != MP_OKAY) { goto error; } /* tmp2 = 3*pX^3 */
if (mp_sub(&tmp, &tmp2, &tmp) != MP_OKAY) { goto error; } /* tmp = tmp - tmp2 */
if (mp_add(&tmp, &p, &tmp) != MP_OKAY) { goto error; } /* tmp = tmp + p */
if (mp_read_radix(&p, (unsigned char *)sets[idx].prime, 10) != MP_OKAY) { goto error; } /* p = prime */
if (mp_mod(&tmp, &p, &tmp) != MP_OKAY) { goto error; } /* tmp = tmp mod p */
/* now find square root */
if (mp_add_d(&p, 1, &tmp2) != MP_OKAY) { goto error; } /* tmp2 = p + 1 */
if (mp_div_2(&tmp2, &tmp2) != MP_OKAY) { goto error; } /* tmp2 = tmp2/2 */
if (mp_div_2(&tmp2, &tmp2) != MP_OKAY) { goto error; } /* tmp2 = (p+1)/4 */
if (mp_exptmod(&tmp, &tmp2, &p, &tmp) != MP_OKAY) { goto error; } /* tmp = (x^3 - 3x + b)^((p+1)/4) mod p */
/* if result==0, then y==tmp, otherwise y==p-tmp */
if (result == 0) {
if (mp_copy(&tmp, &pt->y) != MP_OKAY) { goto error; }
} else {
if (mp_sub(&p, &tmp, &pt->y) != MP_OKAY) { goto error; }
}
res = CRYPT_OK;
goto done;
error:
res = CRYPT_MEM;
done:
mp_clear_multi(&p, &tmp, &tmp2, NULL);
return res;
}
#define OUTPUT_BIGNUM(num, buf2, y, z) \
{ \
z = mp_raw_size(num); \
STORE32L(z, buf2+y); \
y += 4; \
mp_toraw(num, buf2+y); \
y += z; \
}
#define INPUT_BIGNUM(num, in, x, y) \
{ \
/* load value */ \
LOAD32L(x, in+y); \
y += 4; \
\
/* sanity check... */ \
if (x > 1024) { \
goto error; \
} \
\
/* load it */ \
if (mp_read_raw(num, (unsigned char *)in+y, x) != MP_OKAY) {\
goto error; \
} \
y += x; \
}
int ecc_export(unsigned char *out, unsigned long *outlen, int type, ecc_key *key)
{
unsigned long y, z;
int res, errno;
unsigned char buf2[512];
_ARGCHK(out != NULL);
_ARGCHK(outlen != NULL);
_ARGCHK(key != NULL);
/* type valid? */
if (key->type != PK_PRIVATE && type == PK_PRIVATE) {
return CRYPT_PK_TYPE_MISMATCH;
}
/* output type and magic byte */
y = PACKET_SIZE;
buf2[y++] = type;
buf2[y++] = sets[key->idx].size;
/* output x coordinate */
OUTPUT_BIGNUM(&(key->pubkey.x), buf2, y, z);
/* compress y and output it */
if ((errno = compress_y_point(&key->pubkey, key->idx, &res)) != CRYPT_OK) {
return errno;
}
buf2[y++] = res;
if (type == PK_PRIVATE) {
OUTPUT_BIGNUM(&key->k, buf2, y, z);
}
/* check size */
if (*outlen < y) {
return CRYPT_BUFFER_OVERFLOW;
}
/* store header */
packet_store_header(buf2, PACKET_SECT_ECC, PACKET_SUB_KEY, y);
memcpy(out, buf2, y);
*outlen = y;
#ifdef CLEAN_STACK
zeromem(buf2, sizeof(buf2));
#endif
return CRYPT_OK;
}
int ecc_import(const unsigned char *in, ecc_key *key)
{
unsigned long x, y, s;
int res, errno;
_ARGCHK(in != NULL);
_ARGCHK(key != NULL);
/* check type */
if ((errno = packet_valid_header((unsigned char *)in, PACKET_SECT_ECC, PACKET_SUB_KEY)) != CRYPT_OK) {
return errno;
}
/* init key */
if (mp_init_multi(&key->pubkey.x, &key->pubkey.y, &key->k, NULL) != MP_OKAY) {
return CRYPT_MEM;
}
y = PACKET_SIZE;
key->type = in[y++];
s = in[y++];
for (x = 0; (s > (unsigned long)sets[x].size) && (sets[x].size); x++);
if (sets[x].size == 0) {
res = CRYPT_INVALID_KEYSIZE;
goto error2;
}
key->idx = x;
/* type check both values */
if ((key->type != PK_PUBLIC) && (key->type != PK_PRIVATE)) {
res = CRYPT_INVALID_PACKET;
goto error2;
}
/* is the key idx valid? */
if (!is_valid_idx(key->idx)) {
res = CRYPT_INVALID_PACKET;
goto error2;
}
/* load x coordinate */
INPUT_BIGNUM(&key->pubkey.x, in, x, y);
/* load y */
x = in[y++];
if ((errno = expand_y_point(&key->pubkey, key->idx, x)) != CRYPT_OK) { res = errno; goto error2; }
if (key->type == PK_PRIVATE) {
/* load private key */
INPUT_BIGNUM(&key->k, in, x, y);
}
res = CRYPT_OK;
goto done;
error:
res = CRYPT_MEM;
error2:
mp_clear_multi(&key->pubkey.x, &key->pubkey.y, &key->k, NULL);
done:
return res;
}
int ecc_shared_secret(ecc_key *private_key, ecc_key *public_key,
unsigned char *out, unsigned long *outlen)
{
unsigned long x, y;
ecc_point *result;
mp_int prime;
int res, errno;
_ARGCHK(private_key != NULL);
_ARGCHK(public_key != NULL);
_ARGCHK(out != NULL);
_ARGCHK(outlen != NULL);
/* type valid? */
if (private_key->type != PK_PRIVATE) {
return CRYPT_PK_NOT_PRIVATE;
}
if (private_key->idx != public_key->idx) {
return CRYPT_PK_TYPE_MISMATCH;
}
/* make new point */
result = new_point();
if (result == NULL) {
return CRYPT_MEM;
}
if (mp_init(&prime) != MP_OKAY) {
del_point(result);
return CRYPT_MEM;
}
if (mp_read_radix(&prime, (unsigned char *)sets[private_key->idx].prime, 10) != MP_OKAY) { goto error; }
if ((errno = ecc_mulmod(&private_key->k, &public_key->pubkey, result, &prime, private_key->idx)) != CRYPT_OK) { res = errno; goto done1; }
x = mp_raw_size(&result->x);
y = mp_raw_size(&result->y);
if (*outlen < (x+y)) {
res = CRYPT_BUFFER_OVERFLOW;
goto done1;
}
*outlen = x+y;
mp_toraw(&result->x, out);
mp_toraw(&result->y, out+x);
res = CRYPT_OK;
goto done1;
error:
res = CRYPT_MEM;
done1:
mp_clear(&prime);
del_point(result);
return res;
}
int ecc_get_size(ecc_key *key)
{
_ARGCHK(key != NULL);
if (is_valid_idx(key->idx))
return sets[key->idx].size;
else
return INT_MAX; /* large value known to cause it to fail when passed to ecc_make_key() */
}
#include "ecc_sys.c"
#endif
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