diff options
Diffstat (limited to 'libtomcrypt/src/pk/ecc/ltc_ecc_mul2add.c')
| -rw-r--r-- | libtomcrypt/src/pk/ecc/ltc_ecc_mul2add.c | 207 |
1 files changed, 207 insertions, 0 deletions
diff --git a/libtomcrypt/src/pk/ecc/ltc_ecc_mul2add.c b/libtomcrypt/src/pk/ecc/ltc_ecc_mul2add.c new file mode 100644 index 0000000..ac1c24f --- /dev/null +++ b/libtomcrypt/src/pk/ecc/ltc_ecc_mul2add.c @@ -0,0 +1,207 @@ +/* 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_mul2add.c + ECC Crypto, Shamir's Trick, Tom St Denis +*/ + +#ifdef MECC + +#ifdef LTC_ECC_SHAMIR + +/** Computes kA*A + kB*B = C using Shamir's Trick + @param A First point to multiply + @param kA What to multiple A by + @param B Second point to multiply + @param kB What to multiple B by + @param C [out] Destination point (can overlap with A or B + @param modulus Modulus for curve + @return CRYPT_OK on success +*/ +int ltc_ecc_mul2add(ecc_point *A, void *kA, + ecc_point *B, void *kB, + ecc_point *C, + void *modulus) +{ + ecc_point *precomp[16]; + unsigned bitbufA, bitbufB, lenA, lenB, len, x, y, nA, nB, nibble; + unsigned char *tA, *tB; + int err, first; + void *mp, *mu; + + /* argchks */ + LTC_ARGCHK(A != NULL); + LTC_ARGCHK(B != NULL); + LTC_ARGCHK(C != NULL); + LTC_ARGCHK(kA != NULL); + LTC_ARGCHK(kB != NULL); + LTC_ARGCHK(modulus != NULL); + + /* allocate memory */ + tA = XCALLOC(1, ECC_BUF_SIZE); + if (tA == NULL) { + return CRYPT_MEM; + } + tB = XCALLOC(1, ECC_BUF_SIZE); + if (tB == NULL) { + XFREE(tA); + return CRYPT_MEM; + } + + /* get sizes */ + lenA = mp_unsigned_bin_size(kA); + lenB = mp_unsigned_bin_size(kB); + len = MAX(lenA, lenB); + + /* sanity check */ + if ((lenA > ECC_BUF_SIZE) || (lenB > ECC_BUF_SIZE)) { + err = CRYPT_INVALID_ARG; + goto ERR_T; + } + + /* extract and justify kA */ + mp_to_unsigned_bin(kA, (len - lenA) + tA); + + /* extract and justify kB */ + mp_to_unsigned_bin(kB, (len - lenB) + tB); + + /* allocate the table */ + for (x = 0; x < 16; x++) { + precomp[x] = ltc_ecc_new_point(); + if (precomp[x] == NULL) { + for (y = 0; y < x; ++y) { + ltc_ecc_del_point(precomp[y]); + } + err = CRYPT_MEM; + goto ERR_T; + } + } + + /* init montgomery reduction */ + if ((err = mp_montgomery_setup(modulus, &mp)) != CRYPT_OK) { + goto ERR_P; + } + if ((err = mp_init(&mu)) != CRYPT_OK) { + goto ERR_MP; + } + if ((err = mp_montgomery_normalization(mu, modulus)) != CRYPT_OK) { + goto ERR_MU; + } + + /* copy ones ... */ + if ((err = mp_mulmod(A->x, mu, modulus, precomp[1]->x)) != CRYPT_OK) { goto ERR_MU; } + if ((err = mp_mulmod(A->y, mu, modulus, precomp[1]->y)) != CRYPT_OK) { goto ERR_MU; } + if ((err = mp_mulmod(A->z, mu, modulus, precomp[1]->z)) != CRYPT_OK) { goto ERR_MU; } + + if ((err = mp_mulmod(B->x, mu, modulus, precomp[1<<2]->x)) != CRYPT_OK) { goto ERR_MU; } + if ((err = mp_mulmod(B->y, mu, modulus, precomp[1<<2]->y)) != CRYPT_OK) { goto ERR_MU; } + if ((err = mp_mulmod(B->z, mu, modulus, precomp[1<<2]->z)) != CRYPT_OK) { goto ERR_MU; } + + /* precomp [i,0](A + B) table */ + if ((err = ltc_mp.ecc_ptdbl(precomp[1], precomp[2], modulus, mp)) != CRYPT_OK) { goto ERR_MU; } + if ((err = ltc_mp.ecc_ptadd(precomp[1], precomp[2], precomp[3], modulus, mp)) != CRYPT_OK) { goto ERR_MU; } + + /* precomp [0,i](A + B) table */ + if ((err = ltc_mp.ecc_ptdbl(precomp[1<<2], precomp[2<<2], modulus, mp)) != CRYPT_OK) { goto ERR_MU; } + if ((err = ltc_mp.ecc_ptadd(precomp[1<<2], precomp[2<<2], precomp[3<<2], modulus, mp)) != CRYPT_OK) { goto ERR_MU; } + + /* precomp [i,j](A + B) table (i != 0, j != 0) */ + for (x = 1; x < 4; x++) { + for (y = 1; y < 4; y++) { + if ((err = ltc_mp.ecc_ptadd(precomp[x], precomp[(y<<2)], precomp[x+(y<<2)], modulus, mp)) != CRYPT_OK) { goto ERR_MU; } + } + } + + nibble = 3; + first = 1; + bitbufA = tA[0]; + bitbufB = tB[0]; + + /* for every byte of the multiplicands */ + for (x = -1;; ) { + /* grab a nibble */ + if (++nibble == 4) { + ++x; if (x == len) break; + bitbufA = tA[x]; + bitbufB = tB[x]; + nibble = 0; + } + + /* extract two bits from both, shift/update */ + nA = (bitbufA >> 6) & 0x03; + nB = (bitbufB >> 6) & 0x03; + bitbufA = (bitbufA << 2) & 0xFF; + bitbufB = (bitbufB << 2) & 0xFF; + + /* if both zero, if first, continue */ + if ((nA == 0) && (nB == 0) && (first == 1)) { + continue; + } + + /* double twice, only if this isn't the first */ + if (first == 0) { + /* double twice */ + if ((err = ltc_mp.ecc_ptdbl(C, C, modulus, mp)) != CRYPT_OK) { goto ERR_MU; } + if ((err = ltc_mp.ecc_ptdbl(C, C, modulus, mp)) != CRYPT_OK) { goto ERR_MU; } + } + + /* if not both zero */ + if ((nA != 0) || (nB != 0)) { + if (first == 1) { + /* if first, copy from table */ + first = 0; + if ((err = mp_copy(precomp[nA + (nB<<2)]->x, C->x)) != CRYPT_OK) { goto ERR_MU; } + if ((err = mp_copy(precomp[nA + (nB<<2)]->y, C->y)) != CRYPT_OK) { goto ERR_MU; } + if ((err = mp_copy(precomp[nA + (nB<<2)]->z, C->z)) != CRYPT_OK) { goto ERR_MU; } + } else { + /* if not first, add from table */ + if ((err = ltc_mp.ecc_ptadd(C, precomp[nA + (nB<<2)], C, modulus, mp)) != CRYPT_OK) { goto ERR_MU; } + } + } + } + + /* reduce to affine */ + err = ltc_ecc_map(C, modulus, mp); + + /* clean up */ +ERR_MU: + mp_clear(mu); +ERR_MP: + mp_montgomery_free(mp); +ERR_P: + for (x = 0; x < 16; x++) { + ltc_ecc_del_point(precomp[x]); + } +ERR_T: +#ifdef LTC_CLEAN_STACK + zeromem(tA, ECC_BUF_SIZE); + zeromem(tB, ECC_BUF_SIZE); +#endif + XFREE(tA); + XFREE(tB); + + return err; +} + +#endif +#endif + +/* $Source: /cvs/libtom/libtomcrypt/src/pk/ecc/ltc_ecc_mul2add.c,v $ */ +/* $Revision: 1.6 $ */ +/* $Date: 2006/12/04 05:07:59 $ */ |