Mercurial > dropbear
view libtomcrypt/src/pk/ecc/ltc_ecc_mulmod_timing.c @ 549:7f552ea5bf72 maemo
merge of '3450609f92928775614418f40dd44ed5393d9de4'
and '6a58c90036c543b4d992489843a999156f665e61'
author | Matt Johnston <matt@ucc.asn.au> |
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date | Wed, 01 Jul 2009 05:14:51 +0000 |
parents | 0cbe8f6dbf9e |
children | 0e1465709336 |
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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. * * Tom St Denis, [email protected], http://libtomcrypt.com */ /* 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 "tomcrypt.h" /** @file ltc_ecc_mulmod_timing.c ECC Crypto, Tom St Denis */ #ifdef MECC #ifdef LTC_ECC_TIMING_RESISTANT /** Perform a point multiplication (timing resistant) @param k The scalar to multiply by @param G The base point @param R [out] Destination for kG @param modulus The modulus of the field the ECC curve is in @param map Boolean whether to map back to affine or not (1==map, 0 == leave in projective) @return CRYPT_OK on success */ int ltc_ecc_mulmod(void *k, ecc_point *G, ecc_point *R, void *modulus, int map) { ecc_point *tG, *M[3]; int i, j, err; void *mu, *mp; unsigned long buf; int first, bitbuf, bitcpy, bitcnt, mode, digidx; LTC_ARGCHK(k != NULL); LTC_ARGCHK(G != NULL); LTC_ARGCHK(R != NULL); LTC_ARGCHK(modulus != NULL); /* init montgomery reduction */ if ((err = mp_montgomery_setup(modulus, &mp)) != CRYPT_OK) { return err; } if ((err = mp_init(&mu)) != CRYPT_OK) { mp_montgomery_free(mp); return err; } if ((err = mp_montgomery_normalization(mu, modulus)) != CRYPT_OK) { mp_clear(mu); mp_montgomery_free(mp); return err; } /* alloc ram for window temps */ for (i = 0; i < 3; i++) { M[i] = ltc_ecc_new_point(); if (M[i] == NULL) { for (j = 0; j < i; j++) { ltc_ecc_del_point(M[j]); } mp_clear(mu); mp_montgomery_free(mp); return CRYPT_MEM; } } /* make a copy of G incase R==G */ tG = ltc_ecc_new_point(); if (tG == NULL) { err = CRYPT_MEM; goto done; } /* tG = G and convert to montgomery */ if ((err = mp_mulmod(G->x, mu, modulus, tG->x)) != CRYPT_OK) { goto done; } if ((err = mp_mulmod(G->y, mu, modulus, tG->y)) != CRYPT_OK) { goto done; } if ((err = mp_mulmod(G->z, mu, modulus, tG->z)) != CRYPT_OK) { goto done; } mp_clear(mu); mu = NULL; /* calc the M tab */ /* M[0] == G */ if ((err = mp_copy(tG->x, M[0]->x)) != CRYPT_OK) { goto done; } if ((err = mp_copy(tG->y, M[0]->y)) != CRYPT_OK) { goto done; } if ((err = mp_copy(tG->z, M[0]->z)) != CRYPT_OK) { goto done; } /* M[1] == 2G */ if ((err = ltc_mp.ecc_ptdbl(tG, M[1], modulus, mp)) != CRYPT_OK) { goto done; } /* setup sliding window */ mode = 0; bitcnt = 1; buf = 0; digidx = mp_get_digit_count(k) - 1; bitcpy = bitbuf = 0; first = 1; /* perform ops */ for (;;) { /* grab next digit as required */ if (--bitcnt == 0) { if (digidx == -1) { break; } buf = mp_get_digit(k, digidx); bitcnt = (int) MP_DIGIT_BIT; --digidx; } /* grab the next msb from the ltiplicand */ i = (buf >> (MP_DIGIT_BIT - 1)) & 1; buf <<= 1; if (mode == 0 && i == 0) { /* dummy operations */ if ((err = ltc_mp.ecc_ptadd(M[0], M[1], M[2], modulus, mp)) != CRYPT_OK) { goto done; } if ((err = ltc_mp.ecc_ptdbl(M[1], M[2], modulus, mp)) != CRYPT_OK) { goto done; } continue; } if (mode == 0 && i == 1) { mode = 1; /* dummy operations */ if ((err = ltc_mp.ecc_ptadd(M[0], M[1], M[2], modulus, mp)) != CRYPT_OK) { goto done; } if ((err = ltc_mp.ecc_ptdbl(M[1], M[2], modulus, mp)) != CRYPT_OK) { goto done; } continue; } if ((err = ltc_mp.ecc_ptadd(M[0], M[1], M[i^1], modulus, mp)) != CRYPT_OK) { goto done; } if ((err = ltc_mp.ecc_ptdbl(M[i], M[i], modulus, mp)) != CRYPT_OK) { goto done; } } /* copy result out */ if ((err = mp_copy(M[0]->x, R->x)) != CRYPT_OK) { goto done; } if ((err = mp_copy(M[0]->y, R->y)) != CRYPT_OK) { goto done; } if ((err = mp_copy(M[0]->z, R->z)) != CRYPT_OK) { goto done; } /* map R back from projective space */ if (map) { err = ltc_ecc_map(R, modulus, mp); } else { err = CRYPT_OK; } done: if (mu != NULL) { mp_clear(mu); } mp_montgomery_free(mp); ltc_ecc_del_point(tG); for (i = 0; i < 3; i++) { ltc_ecc_del_point(M[i]); } return err; } #endif #endif /* $Source: /cvs/libtom/libtomcrypt/src/pk/ecc/ltc_ecc_mulmod_timing.c,v $ */ /* $Revision: 1.11 $ */ /* $Date: 2006/12/04 22:17:46 $ */