--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtomcrypt/src/pk/rsa/rsa_make_key.c	Wed Mar 08 13:23:58 2006 +0000
@@ -0,0 +1,125 @@
+/* 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 rsa_make_key.c
+  RSA key generation, Tom St Denis
+*/  
+
+#ifdef MRSA
+
+/** 
+   Create an RSA key
+   @param prng     An active PRNG state
+   @param wprng    The index of the PRNG desired
+   @param size     The size of the modulus (key size) desired (octets)
+   @param e        The "e" value (public key).  e==65537 is a good choice
+   @param key      [out] Destination of a newly created private key pair
+   @return CRYPT_OK if successful, upon error all allocated ram is freed
+*/
+int rsa_make_key(prng_state *prng, int wprng, int size, long e, rsa_key *key)
+{
+   mp_int p, q, tmp1, tmp2, tmp3;
+   int    err;
+
+   LTC_ARGCHK(key != NULL);
+
+   if ((size < (MIN_RSA_SIZE/8)) || (size > (MAX_RSA_SIZE/8))) {
+      return CRYPT_INVALID_KEYSIZE;
+   }
+
+   if ((e < 3) || ((e & 1) == 0)) {
+      return CRYPT_INVALID_ARG;
+   }
+
+   if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
+      return err;
+   }
+
+   if ((err = mp_init_multi(&p, &q, &tmp1, &tmp2, &tmp3, NULL)) != MP_OKAY) {
+      return mpi_to_ltc_error(err);
+   }
+
+   /* make primes p and q (optimization provided by Wayne Scott) */
+   if ((err = mp_set_int(&tmp3, e)) != MP_OKAY) { goto error; }            /* tmp3 = e */
+
+   /* make prime "p" */
+   do {
+       if ((err = rand_prime(&p, size*4, prng, wprng)) != CRYPT_OK) { goto done; }
+       if ((err = mp_sub_d(&p, 1, &tmp1)) != MP_OKAY)               { goto error; }  /* tmp1 = p-1 */
+       if ((err = mp_gcd(&tmp1, &tmp3, &tmp2)) != MP_OKAY)          { goto error; }  /* tmp2 = gcd(p-1, e) */
+   } while (mp_cmp_d(&tmp2, 1) != 0);                                                /* while e divides p-1 */
+
+   /* make prime "q" */
+   do {
+       if ((err = rand_prime(&q, size*4, prng, wprng)) != CRYPT_OK) { goto done; }
+       if ((err = mp_sub_d(&q, 1, &tmp1)) != MP_OKAY)               { goto error; } /* tmp1 = q-1 */
+       if ((err = mp_gcd(&tmp1, &tmp3, &tmp2)) != MP_OKAY)          { goto error; } /* tmp2 = gcd(q-1, e) */
+   } while (mp_cmp_d(&tmp2, 1) != 0);                                               /* while e divides q-1 */
+
+   /* tmp1 = lcm(p-1, q-1) */
+   if ((err = mp_sub_d(&p, 1, &tmp2)) != MP_OKAY)                  { goto error; } /* tmp2 = p-1 */
+                                                                   /* tmp1 = q-1 (previous do/while loop) */
+   if ((err = mp_lcm(&tmp1, &tmp2, &tmp1)) != MP_OKAY)             { goto error; } /* tmp1 = lcm(p-1, q-1) */
+
+   /* make key */
+   if ((err = mp_init_multi(&key->e, &key->d, &key->N, &key->dQ, &key->dP,
+                     &key->qP, &key->p, &key->q, NULL)) != MP_OKAY) {
+      goto error;
+   }
+
+   if ((err = mp_set_int(&key->e, e)) != MP_OKAY)                     { goto error2; } /* key->e =  e */
+   if ((err = mp_invmod(&key->e, &tmp1, &key->d)) != MP_OKAY)         { goto error2; } /* key->d = 1/e mod lcm(p-1,q-1) */
+   if ((err = mp_mul(&p, &q, &key->N)) != MP_OKAY)                    { goto error2; } /* key->N = pq */
+
+   /* optimize for CRT now */
+   /* find d mod q-1 and d mod p-1 */
+   if ((err = mp_sub_d(&p, 1, &tmp1)) != MP_OKAY)                     { goto error2; } /* tmp1 = q-1 */
+   if ((err = mp_sub_d(&q, 1, &tmp2)) != MP_OKAY)                     { goto error2; } /* tmp2 = p-1 */
+   if ((err = mp_mod(&key->d, &tmp1, &key->dP)) != MP_OKAY)           { goto error2; } /* dP = d mod p-1 */
+   if ((err = mp_mod(&key->d, &tmp2, &key->dQ)) != MP_OKAY)           { goto error2; } /* dQ = d mod q-1 */
+   if ((err = mp_invmod(&q, &p, &key->qP)) != MP_OKAY)                { goto error2; } /* qP = 1/q mod p */
+
+   if ((err = mp_copy(&p, &key->p)) != MP_OKAY)                       { goto error2; }
+   if ((err = mp_copy(&q, &key->q)) != MP_OKAY)                       { goto error2; }
+
+   /* shrink ram required  */
+   if ((err = mp_shrink(&key->e)) != MP_OKAY)                         { goto error2; }
+   if ((err = mp_shrink(&key->d)) != MP_OKAY)                         { goto error2; }
+   if ((err = mp_shrink(&key->N)) != MP_OKAY)                         { goto error2; }
+   if ((err = mp_shrink(&key->dQ)) != MP_OKAY)                        { goto error2; }
+   if ((err = mp_shrink(&key->dP)) != MP_OKAY)                        { goto error2; }
+   if ((err = mp_shrink(&key->qP)) != MP_OKAY)                        { goto error2; }
+   if ((err = mp_shrink(&key->p)) != MP_OKAY)                         { goto error2; }
+   if ((err = mp_shrink(&key->q)) != MP_OKAY)                         { goto error2; }
+
+   /* set key type (in this case it's CRT optimized) */
+   key->type = PK_PRIVATE;
+
+   /* return ok and free temps */
+   err       = CRYPT_OK;
+   goto done;
+error2:
+   mp_clear_multi(&key->d, &key->e, &key->N, &key->dQ, &key->dP,
+                  &key->qP, &key->p, &key->q, NULL);
+error:
+   err = mpi_to_ltc_error(err);
+done:
+   mp_clear_multi(&tmp3, &tmp2, &tmp1, &p, &q, NULL);
+   return err;
+}
+
+#endif
+
+/* $Source: /cvs/libtom/libtomcrypt/src/pk/rsa/rsa_make_key.c,v $ */
+/* $Revision: 1.3 $ */
+/* $Date: 2005/05/05 14:35:59 $ */