diff options
Diffstat (limited to 'libtomcrypt/src/pk/rsa/rsa_exptmod.c')
| -rw-r--r-- | libtomcrypt/src/pk/rsa/rsa_exptmod.c | 115 |
1 files changed, 115 insertions, 0 deletions
diff --git a/libtomcrypt/src/pk/rsa/rsa_exptmod.c b/libtomcrypt/src/pk/rsa/rsa_exptmod.c new file mode 100644 index 0000000..379404c --- /dev/null +++ b/libtomcrypt/src/pk/rsa/rsa_exptmod.c @@ -0,0 +1,115 @@ +/* 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.org + */ +#include "tomcrypt.h" + +/** + @file rsa_exptmod.c + RSA PKCS exptmod, Tom St Denis +*/ + +#ifdef MRSA + +/** + Compute an RSA modular exponentiation + @param in The input data to send into RSA + @param inlen The length of the input (octets) + @param out [out] The destination + @param outlen [in/out] The max size and resulting size of the output + @param which Which exponent to use, e.g. PK_PRIVATE or PK_PUBLIC + @param key The RSA key to use + @return CRYPT_OK if successful +*/ +int rsa_exptmod(const unsigned char *in, unsigned long inlen, + unsigned char *out, unsigned long *outlen, int which, + rsa_key *key) +{ + mp_int tmp, tmpa, tmpb; + unsigned long x; + int err; + + LTC_ARGCHK(in != NULL); + LTC_ARGCHK(out != NULL); + LTC_ARGCHK(outlen != NULL); + LTC_ARGCHK(key != NULL); + + /* is the key of the right type for the operation? */ + if (which == PK_PRIVATE && (key->type != PK_PRIVATE)) { + return CRYPT_PK_NOT_PRIVATE; + } + + /* must be a private or public operation */ + if (which != PK_PRIVATE && which != PK_PUBLIC) { + return CRYPT_PK_INVALID_TYPE; + } + + /* init and copy into tmp */ + if ((err = mp_init_multi(&tmp, &tmpa, &tmpb, NULL)) != MP_OKAY) { return mpi_to_ltc_error(err); } + if ((err = mp_read_unsigned_bin(&tmp, (unsigned char *)in, (int)inlen)) != MP_OKAY) { goto error; } + + /* sanity check on the input */ + if (mp_cmp(&key->N, &tmp) == MP_LT) { + err = CRYPT_PK_INVALID_SIZE; + goto done; + } + + /* are we using the private exponent and is the key optimized? */ + if (which == PK_PRIVATE) { + /* tmpa = tmp^dP mod p */ + if ((err = mp_exptmod(&tmp, &key->dP, &key->p, &tmpa)) != MP_OKAY) { goto error; } + + /* tmpb = tmp^dQ mod q */ + if ((err = mp_exptmod(&tmp, &key->dQ, &key->q, &tmpb)) != MP_OKAY) { goto error; } + + /* tmp = (tmpa - tmpb) * qInv (mod p) */ + if ((err = mp_sub(&tmpa, &tmpb, &tmp)) != MP_OKAY) { goto error; } + if ((err = mp_mulmod(&tmp, &key->qP, &key->p, &tmp)) != MP_OKAY) { goto error; } + + /* tmp = tmpb + q * tmp */ + if ((err = mp_mul(&tmp, &key->q, &tmp)) != MP_OKAY) { goto error; } + if ((err = mp_add(&tmp, &tmpb, &tmp)) != MP_OKAY) { goto error; } + } else { + /* exptmod it */ + if ((err = mp_exptmod(&tmp, &key->e, &key->N, &tmp)) != MP_OKAY) { goto error; } + } + + /* read it back */ + x = (unsigned long)mp_unsigned_bin_size(&key->N); + if (x > *outlen) { + err = CRYPT_BUFFER_OVERFLOW; + goto done; + } + + /* this should never happen ... */ + if (mp_unsigned_bin_size(&tmp) > mp_unsigned_bin_size(&key->N)) { + err = CRYPT_ERROR; + goto done; + } + *outlen = x; + + /* convert it */ + zeromem(out, x); + if ((err = mp_to_unsigned_bin(&tmp, out+(x-mp_unsigned_bin_size(&tmp)))) != MP_OKAY) { goto error; } + + /* clean up and return */ + err = CRYPT_OK; + goto done; +error: + err = mpi_to_ltc_error(err); +done: + mp_clear_multi(&tmp, &tmpa, &tmpb, NULL); + return err; +} + +#endif + +/* $Source: /cvs/libtom/libtomcrypt/src/pk/rsa/rsa_exptmod.c,v $ */ +/* $Revision: 1.4 $ */ +/* $Date: 2005/06/23 02:10:22 $ */ |