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/* LibTomCrypt, modular cryptographic library -- Tom St Denis
*
* LibTomCrypt is a library that provides various cryptographic
* algorithms in a highly modular and flexible manner.
*
* The library is free for all purposes without any express
* guarantee it works.
*/
#include "tomcrypt.h"
#ifdef LTC_MECC
int ltc_ecc_import_point(const unsigned char *in, unsigned long inlen, void *prime, void *a, void *b, void *x, void *y)
{
int err;
unsigned long size;
void *t1, *t2;
/* init key + temporary numbers */
if (mp_init_multi(&t1, &t2, NULL) != CRYPT_OK) {
return CRYPT_MEM;
}
size = mp_unsigned_bin_size(prime);
if (in[0] == 0x04 && (inlen&1) && ((inlen-1)>>1) == size) {
/* read uncompressed point */
/* load x */
if ((err = mp_read_unsigned_bin(x, (unsigned char *)in+1, size)) != CRYPT_OK) { goto cleanup; }
/* load y */
if ((err = mp_read_unsigned_bin(y, (unsigned char *)in+1+size, size)) != CRYPT_OK) { goto cleanup; }
}
else if ((in[0] == 0x02 || in[0] == 0x03) && (inlen-1) == size) {
/* read compressed point */
/* load x */
if ((err = mp_read_unsigned_bin(x, (unsigned char *)in+1, size)) != CRYPT_OK) { goto cleanup; }
/* compute x^3 */
if ((err = mp_sqr(x, t1)) != CRYPT_OK) { goto cleanup; }
if ((err = mp_mulmod(t1, x, prime, t1)) != CRYPT_OK) { goto cleanup; }
/* compute x^3 + a*x */
if ((err = mp_mulmod(a, x, prime, t2)) != CRYPT_OK) { goto cleanup; }
if ((err = mp_add(t1, t2, t1)) != CRYPT_OK) { goto cleanup; }
/* compute x^3 + a*x + b */
if ((err = mp_add(t1, b, t1)) != CRYPT_OK) { goto cleanup; }
/* compute sqrt(x^3 + a*x + b) */
if ((err = mp_sqrtmod_prime(t1, prime, t2)) != CRYPT_OK) { goto cleanup; }
/* adjust y */
if ((mp_isodd(t2) && in[0] == 0x03) || (!mp_isodd(t2) && in[0] == 0x02)) {
if ((err = mp_mod(t2, prime, y)) != CRYPT_OK) { goto cleanup; }
}
else {
if ((err = mp_submod(prime, t2, prime, y)) != CRYPT_OK) { goto cleanup; }
}
}
else {
err = CRYPT_INVALID_PACKET;
goto cleanup;
}
err = CRYPT_OK;
cleanup:
mp_clear_multi(t1, t2, NULL);
return err;
}
#endif
/* ref: $Format:%D$ */
/* git commit: $Format:%H$ */
/* commit time: $Format:%ai$ */
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