diff options
Diffstat (limited to 'src/pk/ecc/ltc_ecc_mulmod_timing.c')
| -rw-r--r-- | src/pk/ecc/ltc_ecc_mulmod_timing.c | 167 |
1 files changed, 167 insertions, 0 deletions
diff --git a/src/pk/ecc/ltc_ecc_mulmod_timing.c b/src/pk/ecc/ltc_ecc_mulmod_timing.c new file mode 100644 index 0000000..b94a50c --- /dev/null +++ b/src/pk/ecc/ltc_ecc_mulmod_timing.c @@ -0,0 +1,167 @@ +/* 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, tomstdenis@gmail.com, 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 $ */ + |