Mercurial > dropbear
view src/pk/rsa/rsa_exptmod.c @ 222:36160290a1b2 libtomcrypt LTC_DB_0.46
* change include path of options.h
* don't use the constant ROL/ROR operations, since compilers
seem to have problems
author | Matt Johnston <matt@ucc.asn.au> |
---|---|
date | Fri, 08 Jul 2005 19:13:24 +0000 |
parents | 39d5d58461d6 |
children |
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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.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 $ */