libtom.libtomcrypt/rsa_encrypt_key.c

/* 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 "mycrypt.h"

#ifdef MRSA

/* (PKCS #1 v2.0) OAEP pad then encrypt */
int rsa_encrypt_key(const unsigned char *inkey,  unsigned long inlen,
                          unsigned char *outkey, unsigned long *outlen,
                    const unsigned char *lparam, unsigned long lparamlen,
                    prng_state *prng, int prng_idx, int hash_idx, rsa_key *key)
{
  unsigned long modulus_bitlen, modulus_bytelen, x;
  int           err;
  
  _ARGCHK(inkey  != NULL);
  _ARGCHK(outkey != NULL);
  _ARGCHK(outlen != NULL);
  _ARGCHK(key    != NULL);
  
  /* valid prng and hash ? */
  if ((err = prng_is_valid(prng_idx)) != CRYPT_OK) {
     return err;
  }
  if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) {
     return err;
  }
  
  /* get modulus len in bits */
  modulus_bitlen = mp_count_bits(&(key->N));

  /* outlen must be at least the size of the modulus */
  modulus_bytelen = mp_unsigned_bin_size(&(key->N));
  if (modulus_bytelen > *outlen) {
     return CRYPT_BUFFER_OVERFLOW;
  }
      
  /* OAEP pad the key */
  x = *outlen;
  if ((err = pkcs_1_oaep_encode(inkey, inlen, lparam, 
                                lparamlen, modulus_bitlen, prng, prng_idx, hash_idx, 
                                outkey, &x)) != CRYPT_OK) {
     return err;
  }                                

  /* rsa exptmod the OAEP pad */
  return rsa_exptmod(outkey, x, outkey, outlen, PK_PUBLIC, prng, prng_idx, key);
}

#endif /* MRSA */