--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtomcrypt/src/pk/dsa/dsa_encrypt_key.c	Sun Sep 14 06:47:51 2008 +0000
@@ -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, [email protected], 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 $ */
+