diff options
Diffstat (limited to 'src/pk/dsa/dsa_encrypt_key.c')
| -rw-r--r-- | src/pk/dsa/dsa_encrypt_key.c | 135 |
1 files changed, 135 insertions, 0 deletions
diff --git a/src/pk/dsa/dsa_encrypt_key.c b/src/pk/dsa/dsa_encrypt_key.c new file mode 100644 index 0000000..cefa4de --- /dev/null +++ b/src/pk/dsa/dsa_encrypt_key.c @@ -0,0 +1,135 @@ +/* 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 + */ +#include "tomcrypt.h" + +/** + @file dsa_encrypt_key.c + DSA Crypto, Tom St Denis +*/ + +#ifdef MDSA + +/** + Encrypt a symmetric key with DSA + @param in The symmetric key you want to encrypt + @param inlen The length of the key to encrypt (octets) + @param out [out] The destination for the ciphertext + @param outlen [in/out] The max size and resulting size of the ciphertext + @param prng An active PRNG state + @param wprng The index of the PRNG you wish to use + @param hash The index of the hash you want to use + @param key The DSA key you want to encrypt to + @return CRYPT_OK if successful +*/ +int dsa_encrypt_key(const unsigned char *in, unsigned long inlen, + unsigned char *out, unsigned long *outlen, + prng_state *prng, int wprng, int hash, + dsa_key *key) +{ + unsigned char *expt, *skey; + void *g_pub, *g_priv; + unsigned long x, y; + int err; + + LTC_ARGCHK(in != NULL); + LTC_ARGCHK(out != NULL); + LTC_ARGCHK(outlen != NULL); + LTC_ARGCHK(key != NULL); + + /* check that wprng/cipher/hash are not invalid */ + if ((err = prng_is_valid(wprng)) != CRYPT_OK) { + return err; + } + + if ((err = hash_is_valid(hash)) != CRYPT_OK) { + return err; + } + + if (inlen > hash_descriptor[hash].hashsize) { + return CRYPT_INVALID_HASH; + } + + /* make a random key and export the public copy */ + if ((err = mp_init_multi(&g_pub, &g_priv, NULL)) != CRYPT_OK) { + return err; + } + + expt = XMALLOC(mp_unsigned_bin_size(key->p) + 1); + skey = XMALLOC(MAXBLOCKSIZE); + if (expt == NULL || skey == NULL) { + if (expt != NULL) { + XFREE(expt); + } + if (skey != NULL) { + XFREE(skey); + } + mp_clear_multi(g_pub, g_priv, NULL); + return CRYPT_MEM; + } + + /* make a random x, g^x pair */ + x = mp_unsigned_bin_size(key->q); + if (prng_descriptor[wprng].read(expt, x, prng) != x) { + err = CRYPT_ERROR_READPRNG; + goto LBL_ERR; + } + + /* load x */ + if ((err = mp_read_unsigned_bin(g_priv, expt, x)) != CRYPT_OK) { + goto LBL_ERR; + } + + /* compute y */ + if ((err = mp_exptmod(key->g, g_priv, key->p, g_pub)) != CRYPT_OK) { + goto LBL_ERR; + } + + /* make random key */ + x = mp_unsigned_bin_size(key->p) + 1; + if ((err = dsa_shared_secret(g_priv, key->y, key, expt, &x)) != CRYPT_OK) { + goto LBL_ERR; + } + + y = MAXBLOCKSIZE; + if ((err = hash_memory(hash, expt, x, skey, &y)) != CRYPT_OK) { + goto LBL_ERR; + } + + /* Encrypt key */ + for (x = 0; x < inlen; x++) { + skey[x] ^= in[x]; + } + + err = der_encode_sequence_multi(out, outlen, + LTC_ASN1_OBJECT_IDENTIFIER, hash_descriptor[hash].OIDlen, hash_descriptor[hash].OID, + LTC_ASN1_INTEGER, 1UL, g_pub, + LTC_ASN1_OCTET_STRING, inlen, skey, + LTC_ASN1_EOL, 0UL, NULL); + +LBL_ERR: +#ifdef LTC_CLEAN_STACK + /* clean up */ + zeromem(expt, mp_unsigned_bin_size(key->p) + 1); + zeromem(skey, MAXBLOCKSIZE); +#endif + + XFREE(skey); + XFREE(expt); + + mp_clear_multi(g_pub, g_priv, NULL); + return err; +} + +#endif +/* $Source: /cvs/libtom/libtomcrypt/src/pk/dsa/dsa_encrypt_key.c,v $ */ +/* $Revision: 1.7 $ */ +/* $Date: 2006/12/04 03:18:43 $ */ + |