diff options
Diffstat (limited to 'libtomcrypt/src/pk/ecc/ecc_shared_secret.c')
| -rw-r--r-- | libtomcrypt/src/pk/ecc/ecc_shared_secret.c | 95 |
1 files changed, 95 insertions, 0 deletions
diff --git a/libtomcrypt/src/pk/ecc/ecc_shared_secret.c b/libtomcrypt/src/pk/ecc/ecc_shared_secret.c new file mode 100644 index 0000000..ddef847 --- /dev/null +++ b/libtomcrypt/src/pk/ecc/ecc_shared_secret.c @@ -0,0 +1,95 @@ +/* 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 ecc_shared_secret.c + ECC Crypto, Tom St Denis +*/ + +#ifdef MECC + +/** + Create an ECC shared secret between two keys + @param private_key The private ECC key + @param public_key The public key + @param out [out] Destination of the shared secret (Conforms to EC-DH from ANSI X9.63) + @param outlen [in/out] The max size and resulting size of the shared secret + @return CRYPT_OK if successful +*/ +int ecc_shared_secret(ecc_key *private_key, ecc_key *public_key, + unsigned char *out, unsigned long *outlen) +{ + unsigned long x; + ecc_point *result; + void *prime; + int err; + + LTC_ARGCHK(private_key != NULL); + LTC_ARGCHK(public_key != NULL); + LTC_ARGCHK(out != NULL); + LTC_ARGCHK(outlen != NULL); + + /* type valid? */ + if (private_key->type != PK_PRIVATE) { + return CRYPT_PK_NOT_PRIVATE; + } + + if (ltc_ecc_is_valid_idx(private_key->idx) == 0 || ltc_ecc_is_valid_idx(public_key->idx) == 0) { + return CRYPT_INVALID_ARG; + } + + if (XSTRCMP(private_key->dp->name, public_key->dp->name) != 0) { + return CRYPT_PK_TYPE_MISMATCH; + } + + /* make new point */ + result = ltc_ecc_new_point(); + if (result == NULL) { + return CRYPT_MEM; + } + + if ((err = mp_init(&prime)) != CRYPT_OK) { + ltc_ecc_del_point(result); + return err; + } + + if ((err = mp_read_radix(prime, (char *)private_key->dp->prime, 16)) != CRYPT_OK) { goto done; } + if ((err = ltc_mp.ecc_ptmul(private_key->k, &public_key->pubkey, result, prime, 1)) != CRYPT_OK) { goto done; } + + x = (unsigned long)mp_unsigned_bin_size(prime); + if (*outlen < x) { + *outlen = x; + err = CRYPT_BUFFER_OVERFLOW; + goto done; + } + zeromem(out, x); + if ((err = mp_to_unsigned_bin(result->x, out + (x - mp_unsigned_bin_size(result->x)))) != CRYPT_OK) { goto done; } + + err = CRYPT_OK; + *outlen = x; +done: + mp_clear(prime); + ltc_ecc_del_point(result); + return err; +} + +#endif +/* $Source: /cvs/libtom/libtomcrypt/src/pk/ecc/ecc_shared_secret.c,v $ */ +/* $Revision: 1.8 $ */ +/* $Date: 2006/12/04 02:19:48 $ */ + |