--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtomcrypt/src/pk/dh/dh.c	Sat Mar 25 12:59:58 2006 +0000
@@ -0,0 +1,524 @@
+/* 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 dh.c
+  DH crypto, Tom St Denis
+*/
+  
+#ifdef MDH
+
+/* max export size we'll encounter (smaller than this but lets round up a bit) */
+#define DH_BUF_SIZE 1200
+
+/* This holds the key settings.  ***MUST*** be organized by size from smallest to largest. */
+static const struct {
+    int size;
+    char *name, *base, *prime;
+} sets[] = {
+#ifdef DH768
+{
+   96,
+   "DH-768",
+   "4",
+   "F///////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "//////m3wvV"
+},
+#endif
+#ifdef DH1024
+{
+   128,
+   "DH-1024",
+   "4",
+   "F///////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////m3C47"
+},
+#endif
+#ifdef DH1280
+{
+   160,
+   "DH-1280",
+   "4",
+   "F///////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "//////////////////////////////m4kSN"
+},
+#endif
+#ifdef DH1536
+{
+   192,
+   "DH-1536",
+   "4",
+   "F///////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////m5uqd"
+},
+#endif
+#ifdef DH1792
+{
+   224,
+   "DH-1792",
+   "4",
+   "F///////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "//////////////////////////////////////////////////////mT/sd"
+},
+#endif
+#ifdef DH2048
+{
+   256,
+   "DH-2048",
+   "4",
+   "3///////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "/////////////////////////////////////////m8MPh"
+},
+#endif
+#ifdef DH2560
+{
+   320,
+   "DH-2560",
+   "4",
+   "3///////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "/////mKFpF"
+},
+#endif
+#ifdef DH3072
+{
+   384,
+   "DH-3072",
+   "4",
+   "3///////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "/////////////////////////////m32nN"
+},
+#endif
+#ifdef DH4096
+{
+   512,
+   "DH-4096",
+   "4",
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "/////////////////////m8pOF"
+},
+#endif
+{
+   0,
+   NULL,
+   NULL,
+   NULL
+}
+};
+
+static int is_valid_idx(int n)
+{
+   int x;
+
+   for (x = 0; sets[x].size; x++);
+   if ((n < 0) || (n >= x)) {
+      return 0;
+   }
+   return 1;
+}
+
+/**
+   Test the DH sub-system (can take a while)
+   @return CRYPT_OK if successful
+*/
+int dh_test(void)
+{
+    mp_int p, g, tmp;
+    int x, err, primality;
+
+    if ((err = mp_init_multi(&p, &g, &tmp, NULL)) != MP_OKAY)                 { goto error; }
+
+    for (x = 0; sets[x].size != 0; x++) {
+#if 0
+        printf("dh_test():testing size %d-bits\n", sets[x].size * 8);
+#endif
+        if ((err = mp_read_radix(&g,(char *)sets[x].base, 64)) != MP_OKAY)    { goto error; }
+        if ((err = mp_read_radix(&p,(char *)sets[x].prime, 64)) != MP_OKAY)   { goto error; }
+
+        /* ensure p is prime */
+        if ((err = is_prime(&p, &primality)) != CRYPT_OK)                     { goto done; }
+        if (primality == 0) {
+           err = CRYPT_FAIL_TESTVECTOR;
+           goto done;
+        }
+
+        if ((err = mp_sub_d(&p, 1, &tmp)) != MP_OKAY)                         { goto error; }
+        if ((err = mp_div_2(&tmp, &tmp)) != MP_OKAY)                          { goto error; }
+
+        /* ensure (p-1)/2 is prime */
+        if ((err = is_prime(&tmp, &primality)) != CRYPT_OK)                   { goto done; }
+        if (primality == 0) {
+           err = CRYPT_FAIL_TESTVECTOR;
+           goto done;
+        }
+
+        /* now see if g^((p-1)/2) mod p is in fact 1 */
+        if ((err = mp_exptmod(&g, &tmp, &p, &tmp)) != MP_OKAY)                { goto error; }
+        if (mp_cmp_d(&tmp, 1)) {
+           err = CRYPT_FAIL_TESTVECTOR;
+           goto done;
+        }
+    }
+    err = CRYPT_OK;
+    goto done;
+error:
+    err = mpi_to_ltc_error(err);
+done:
+    mp_clear_multi(&tmp, &g, &p, NULL);
+    return err;
+}
+
+/**
+   Get the min and max DH key sizes (octets)
+   @param low    [out] The smallest key size supported
+   @param high   [out] The largest key size supported
+*/
+void dh_sizes(int *low, int *high)
+{
+   int x;
+   LTC_ARGCHK(low != NULL);
+   LTC_ARGCHK(high != NULL);
+   *low  = INT_MAX;
+   *high = 0;
+   for (x = 0; sets[x].size != 0; x++) {
+       if (*low > sets[x].size)  *low  = sets[x].size;
+       if (*high < sets[x].size) *high = sets[x].size;
+   }
+}
+
+/**
+  Returns the key size of a given DH key (octets)
+  @param key   The DH key to get the size of
+  @return The size if valid or INT_MAX if not
+*/
+int dh_get_size(dh_key *key)
+{
+    LTC_ARGCHK(key != NULL);
+    if (is_valid_idx(key->idx) == 1) {
+        return sets[key->idx].size;
+    } else {
+        return INT_MAX; /* large value that would cause dh_make_key() to fail */
+    }
+}
+
+/**
+  Make a DH key [private key pair]
+  @param prng     An active PRNG state
+  @param wprng    The index for the PRNG you desire to use
+  @param keysize  The key size (octets) desired
+  @param key      [out] Where the newly created DH key will be stored
+  @return CRYPT_OK if successful, note: on error all allocated memory will be freed automatically.
+*/
+int dh_make_key(prng_state *prng, int wprng, int keysize, dh_key *key)
+{
+   unsigned char *buf;
+   unsigned long x;
+   mp_int p, g;
+   int err;
+
+   LTC_ARGCHK(key  != NULL);
+
+   /* good prng? */
+   if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
+      return err;
+   }
+
+   /* find key size */
+   for (x = 0; (keysize > sets[x].size) && (sets[x].size != 0); x++);
+#ifdef FAST_PK
+   keysize = MIN(sets[x].size, 32);
+#else
+   keysize = sets[x].size;
+#endif
+
+   if (sets[x].size == 0) {
+      return CRYPT_INVALID_KEYSIZE;
+   }
+   key->idx = x;
+
+   /* allocate buffer */
+   buf = XMALLOC(keysize);
+   if (buf == NULL) {
+      return CRYPT_MEM;
+   }
+
+   /* make up random string */
+   if (prng_descriptor[wprng].read(buf, keysize, prng) != (unsigned long)keysize) {
+      err = CRYPT_ERROR_READPRNG; 
+      goto error2;
+   }
+
+   /* init parameters */
+   if ((err = mp_init_multi(&g, &p, &key->x, &key->y, NULL)) != MP_OKAY) {
+      goto error;
+   }
+   if ((err = mp_read_radix(&g, sets[key->idx].base, 64)) != MP_OKAY)      { goto error; }
+   if ((err = mp_read_radix(&p, sets[key->idx].prime, 64)) != MP_OKAY)     { goto error; }
+
+   /* load the x value */
+   if ((err = mp_read_unsigned_bin(&key->x, buf, keysize)) != MP_OKAY)     { goto error; }
+   if ((err = mp_exptmod(&g, &key->x, &p, &key->y)) != MP_OKAY)            { goto error; }
+   key->type = PK_PRIVATE;
+
+   if ((err = mp_shrink(&key->x)) != MP_OKAY)                              { goto error; }
+   if ((err = mp_shrink(&key->y)) != MP_OKAY)                              { goto error; }
+
+   /* free up ram */
+   err = CRYPT_OK;
+   goto done;
+error:
+   err = mpi_to_ltc_error(err);
+error2:
+   mp_clear_multi(&key->x, &key->y, NULL);
+done:
+#ifdef LTC_CLEAN_STACK
+   zeromem(buf, keysize);
+#endif
+   mp_clear_multi(&p, &g, NULL);
+   XFREE(buf);
+   return err;
+}
+
+/**
+  Free the allocated ram for a DH key
+  @param key   The key which you wish to free
+*/ 
+void dh_free(dh_key *key)
+{
+   LTC_ARGCHK(key != NULL);
+   mp_clear_multi(&key->x, &key->y, NULL);
+}
+
+/**
+  Export a DH key to a binary packet
+  @param out    [out] The destination for the key
+  @param outlen [in/out] The max size and resulting size of the DH key
+  @param type   Which type of key (PK_PRIVATE or PK_PUBLIC)
+  @param key    The key you wish to export
+  @return CRYPT_OK if successful
+*/
+int dh_export(unsigned char *out, unsigned long *outlen, int type, dh_key *key)
+{
+   unsigned long y, z;
+   int err;
+
+   LTC_ARGCHK(out    != NULL);
+   LTC_ARGCHK(outlen != NULL);
+   LTC_ARGCHK(key    != NULL);
+
+   /* can we store the static header?  */
+   if (*outlen < (PACKET_SIZE + 2)) {
+      return CRYPT_BUFFER_OVERFLOW;
+   }
+   
+   if (type == PK_PRIVATE && key->type != PK_PRIVATE) {
+      return CRYPT_PK_NOT_PRIVATE;
+   }
+
+   /* header */
+   y = PACKET_SIZE;
+
+   /* header */
+   out[y++] = type;
+   out[y++] = (unsigned char)(sets[key->idx].size / 8);
+
+   /* export y */
+   OUTPUT_BIGNUM(&key->y, out, y, z);
+
+   if (type == PK_PRIVATE) {
+      /* export x */
+      OUTPUT_BIGNUM(&key->x, out, y, z);
+   }
+
+   /* store header */
+   packet_store_header(out, PACKET_SECT_DH, PACKET_SUB_KEY);
+
+   /* store len */
+   *outlen = y;
+   return CRYPT_OK;
+}
+
+/**
+  Import a DH key from a binary packet
+  @param in     The packet to read
+  @param inlen  The length of the input packet
+  @param key    [out] Where to import the key to
+  @return CRYPT_OK if successful, on error all allocated memory is freed automatically
+*/
+int dh_import(const unsigned char *in, unsigned long inlen, dh_key *key)
+{
+   unsigned long x, y, s;
+   int err;
+
+   LTC_ARGCHK(in  != NULL);
+   LTC_ARGCHK(key != NULL);
+
+   /* make sure valid length */
+   if ((2+PACKET_SIZE) > inlen) {
+      return CRYPT_INVALID_PACKET;
+   }
+
+   /* check type byte */
+   if ((err = packet_valid_header((unsigned char *)in, PACKET_SECT_DH, PACKET_SUB_KEY)) != CRYPT_OK) {
+      return err;
+   }
+
+   /* init */
+   if ((err = mp_init_multi(&key->x, &key->y, NULL)) != MP_OKAY) {
+      return mpi_to_ltc_error(err);
+   }
+
+   /* advance past packet header */
+   y = PACKET_SIZE;
+
+   /* key type, e.g. private, public */
+   key->type = (int)in[y++];
+
+   /* key size in bytes */
+   s  = (unsigned long)in[y++] * 8;
+
+   for (x = 0; (s > (unsigned long)sets[x].size) && (sets[x].size != 0); x++);
+   if (sets[x].size == 0) {
+      err = CRYPT_INVALID_KEYSIZE;
+      goto error;
+   }
+   key->idx = (int)x;
+
+   /* type check both values */
+   if ((key->type != PK_PUBLIC) && (key->type != PK_PRIVATE))  {
+      err = CRYPT_PK_TYPE_MISMATCH;
+      goto error;
+   }
+
+   /* is the key idx valid? */
+   if (is_valid_idx(key->idx) != 1) {
+      err = CRYPT_PK_TYPE_MISMATCH;
+      goto error;
+   }
+
+   /* load public value g^x mod p*/
+   INPUT_BIGNUM(&key->y, in, x, y, inlen);
+
+   if (key->type == PK_PRIVATE) {
+      INPUT_BIGNUM(&key->x, in, x, y, inlen);
+   }
+
+   /* eliminate private key if public */
+   if (key->type == PK_PUBLIC) {
+      mp_clear(&key->x);
+   }
+
+   return CRYPT_OK;
+error:
+   mp_clear_multi(&key->y, &key->x, NULL);
+   return err;
+}
+
+/**
+   Create a DH shared secret.
+   @param private_key     The private DH key in the pair
+   @param public_key      The public DH key in the pair 
+   @param out             [out] The destination of the shared data
+   @param outlen          [in/out] The max size and resulting size of the shared data.
+   @return CRYPT_OK if successful
+*/
+int dh_shared_secret(dh_key *private_key, dh_key *public_key,
+                     unsigned char *out, unsigned long *outlen)
+{
+   mp_int tmp, p;
+   unsigned long x;
+   int err;
+
+   LTC_ARGCHK(private_key != NULL);
+   LTC_ARGCHK(public_key  != NULL);
+   LTC_ARGCHK(out         != NULL);
+   LTC_ARGCHK(outlen      != NULL);
+
+   /* types valid? */
+   if (private_key->type != PK_PRIVATE) {
+      return CRYPT_PK_NOT_PRIVATE;
+   }
+
+   /* same idx? */
+   if (private_key->idx != public_key->idx) {
+      return CRYPT_PK_TYPE_MISMATCH;
+   }
+
+   /* compute y^x mod p */
+   if ((err = mp_init_multi(&tmp, &p, NULL)) != MP_OKAY) {
+      return mpi_to_ltc_error(err);
+   }
+
+   if ((err = mp_read_radix(&p, (char *)sets[private_key->idx].prime, 64)) != MP_OKAY)     { goto error; }
+   if ((err = mp_exptmod(&public_key->y, &private_key->x, &p, &tmp)) != MP_OKAY)           { goto error; }
+
+   /* enough space for output? */
+   x = (unsigned long)mp_unsigned_bin_size(&tmp);
+   if (*outlen < x) {
+      err = CRYPT_BUFFER_OVERFLOW;
+      goto done;
+   }
+   if ((err = mp_to_unsigned_bin(&tmp, out)) != MP_OKAY)                                   { goto error; }
+   *outlen = x;
+   err = CRYPT_OK;
+   goto done;
+error:
+   err = mpi_to_ltc_error(err);
+done:
+   mp_clear_multi(&p, &tmp, NULL);
+   return err;
+}
+
+#include "dh_sys.c"
+
+#endif
+
+
+/* $Source: /cvs/libtom/libtomcrypt/src/pk/dh/dh.c,v $ */
+/* $Revision: 1.3 $ */
+/* $Date: 2005/05/05 14:35:59 $ */