katja_encrypt_key.c revision f7fc46c63fdc8f39234fea409b8dbe116d73ebf8 
1/* LibTomCrypt, modular cryptographic library -- Tom St Denis
2 *
3 * LibTomCrypt is a library that provides various cryptographic
4 * algorithms in a highly modular and flexible manner.
5 *
6 * The library is free for all purposes without any express
7 * guarantee it works.
8 *
9 * Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.com
10 */
11#include "tomcrypt.h"
12
13/**
14  @file katja_encrypt_key.c
15  Katja PKCS-style OAEP encryption, Tom St Denis
16*/
17
18#ifdef MKAT
19
20/**
21    (PKCS #1 v2.0) OAEP pad then encrypt
22    @param in          The plaintext
23    @param inlen       The length of the plaintext (octets)
24    @param out         [out] The ciphertext
25    @param outlen      [in/out] The max size and resulting size of the ciphertext
26    @param lparam      The system "lparam" for the encryption
27    @param lparamlen   The length of lparam (octets)
28    @param prng        An active PRNG
29    @param prng_idx    The index of the desired prng
30    @param hash_idx    The index of the desired hash
31    @param key         The Katja key to encrypt to
32    @return CRYPT_OK if successful
33*/
34int katja_encrypt_key(const unsigned char *in,     unsigned long inlen,
35                          unsigned char *out,    unsigned long *outlen,
36                    const unsigned char *lparam, unsigned long lparamlen,
37                    prng_state *prng, int prng_idx, int hash_idx, katja_key *key)
38{
39  unsigned long modulus_bitlen, modulus_bytelen, x;
40  int           err;
41
42  LTC_ARGCHK(in     != NULL);
43  LTC_ARGCHK(out    != NULL);
44  LTC_ARGCHK(outlen != NULL);
45  LTC_ARGCHK(key    != NULL);
46
47  /* valid prng and hash ? */
48  if ((err = prng_is_valid(prng_idx)) != CRYPT_OK) {
49     return err;
50  }
51  if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) {
52     return err;
53  }
54
55  /* get modulus len in bits */
56  modulus_bitlen = mp_count_bits((key->N));
57
58  /* payload is upto pq, so we know q is 1/3rd the size of N and therefore pq is 2/3th the size */
59  modulus_bitlen = ((modulus_bitlen << 1) / 3);
60
61  /* round down to next byte */
62  modulus_bitlen -= (modulus_bitlen & 7) + 8;
63
64  /* outlen must be at least the size of the modulus */
65  modulus_bytelen = mp_unsigned_bin_size((key->N));
66  if (modulus_bytelen > *outlen) {
67     *outlen = modulus_bytelen;
68     return CRYPT_BUFFER_OVERFLOW;
69  }
70
71  /* OAEP pad the key */
72  x = *outlen;
73  if ((err = pkcs_1_oaep_encode(in, inlen, lparam,
74                                lparamlen, modulus_bitlen, prng, prng_idx, hash_idx,
75                                out, &x)) != CRYPT_OK) {
76     return err;
77  }
78
79  /* Katja exptmod the OAEP pad */
80  return katja_exptmod(out, x, out, outlen, PK_PUBLIC, key);
81}
82
83#endif /* MRSA */
84
85/* $Source: /cvs/libtom/libtomcrypt/src/pk/katja/katja_encrypt_key.c,v $ */
86/* $Revision: 1.5 $ */
87/* $Date: 2006/06/16 21:53:41 $ */
88