--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtomcrypt/src/pk/pkcs1/pkcs_1_oaep_encode.c	Wed Mar 08 13:23:58 2006 +0000
@@ -0,0 +1,172 @@
+/* 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 pkcs_1_oaep_encode.c
+  OAEP Padding for PKCS #1, Tom St Denis 
+*/
+
+#ifdef PKCS_1
+
+/**
+  PKCS #1 v2.00 OAEP encode
+  @param msg             The data to encode
+  @param msglen          The length of the data to encode (octets)
+  @param lparam          A session or system parameter (can be NULL)
+  @param lparamlen       The length of the lparam data
+  @param modulus_bitlen  The bit length of the RSA modulus
+  @param prng            An active PRNG state
+  @param prng_idx        The index of the PRNG desired
+  @param hash_idx        The index of the hash desired
+  @param out             [out] The destination for the encoded data
+  @param outlen          [in/out] The max size and resulting size of the encoded data
+  @return CRYPT_OK if successful
+*/
+int pkcs_1_oaep_encode(const unsigned char *msg,    unsigned long msglen,
+                       const unsigned char *lparam, unsigned long lparamlen,
+                             unsigned long modulus_bitlen, prng_state *prng,
+                             int           prng_idx,         int  hash_idx,
+                             unsigned char *out,    unsigned long *outlen)
+{
+   unsigned char *DB, *seed, *mask;
+   unsigned long hLen, x, y, modulus_len;
+   int           err;
+
+   LTC_ARGCHK(msg    != NULL);
+   LTC_ARGCHK(out    != NULL);
+   LTC_ARGCHK(outlen != NULL);
+
+   /* test valid hash */
+   if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) { 
+      return err;
+   }
+
+   /* valid prng */
+   if ((err = prng_is_valid(prng_idx)) != CRYPT_OK) {
+      return err;
+   }
+
+   hLen        = hash_descriptor[hash_idx].hashsize;
+   modulus_len = (modulus_bitlen >> 3) + (modulus_bitlen & 7 ? 1 : 0);
+
+   /* test message size */
+   if ((2*hLen >= (modulus_len - 2)) || (msglen > (modulus_len - 2*hLen - 2))) {
+      return CRYPT_PK_INVALID_SIZE;
+   }
+
+   /* allocate ram for DB/mask/salt of size modulus_len */
+   DB   = XMALLOC(modulus_len);
+   mask = XMALLOC(modulus_len);
+   seed = XMALLOC(hLen);
+   if (DB == NULL || mask == NULL || seed == NULL) {
+      if (DB != NULL) {
+         XFREE(DB);
+      }
+      if (mask != NULL) {
+         XFREE(mask);
+      }
+      if (seed != NULL) {
+         XFREE(seed);
+      }
+      return CRYPT_MEM;
+   }
+
+   /* get lhash */
+   /* DB == lhash || PS || 0x01 || M, PS == k - mlen - 2hlen - 2 zeroes */
+   x = modulus_len;
+   if (lparam != NULL) {
+      if ((err = hash_memory(hash_idx, lparam, lparamlen, DB, &x)) != CRYPT_OK) {
+         goto LBL_ERR;
+      }
+   } else {
+      /* can't pass hash_memory a NULL so use DB with zero length */
+      if ((err = hash_memory(hash_idx, DB, 0, DB, &x)) != CRYPT_OK) {
+         goto LBL_ERR;
+      }
+   }
+
+   /* append PS then 0x01 (to lhash)  */
+   x = hLen;
+   y = modulus_len - msglen - 2*hLen - 2;
+   XMEMSET(DB+x, 0, y);
+   x += y;
+
+   /* 0x01 byte */
+   DB[x++] = 0x01;
+
+   /* message (length = msglen) */
+   XMEMCPY(DB+x, msg, msglen);
+   x += msglen;
+
+   /* now choose a random seed */
+   if (prng_descriptor[prng_idx].read(seed, hLen, prng) != hLen) {
+      err = CRYPT_ERROR_READPRNG;
+      goto LBL_ERR;
+   }
+
+   /* compute MGF1 of seed (k - hlen - 1) */
+   if ((err = pkcs_1_mgf1(seed, hLen, hash_idx, mask, modulus_len - hLen - 1)) != CRYPT_OK) {
+      goto LBL_ERR;
+   }
+
+   /* xor against DB */
+   for (y = 0; y < (modulus_len - hLen - 1); y++) {
+       DB[y] ^= mask[y]; 
+   }
+
+   /* compute MGF1 of maskedDB (hLen) */ 
+   if ((err = pkcs_1_mgf1(DB, modulus_len - hLen - 1, hash_idx, mask, hLen)) != CRYPT_OK) {
+      goto LBL_ERR;
+   }
+
+   /* XOR against seed */
+   for (y = 0; y < hLen; y++) {
+      seed[y] ^= mask[y];
+   }
+
+   /* create string of length modulus_len */
+   if (*outlen < modulus_len) {
+      err = CRYPT_BUFFER_OVERFLOW;
+      goto LBL_ERR;
+   }
+
+   /* start output which is 0x00 || maskedSeed || maskedDB */
+   x = 0;
+   out[x++] = 0x00;
+   XMEMCPY(out+x, seed, hLen);
+   x += hLen;
+   XMEMCPY(out+x, DB, modulus_len - hLen - 1);
+   x += modulus_len - hLen - 1;
+
+   *outlen = x;
+    
+   err = CRYPT_OK;
+LBL_ERR:
+#ifdef LTC_CLEAN_STACK
+   zeromem(DB,   modulus_len);
+   zeromem(seed, hLen);
+   zeromem(mask, modulus_len);
+#endif
+
+   XFREE(seed);
+   XFREE(mask);
+   XFREE(DB);
+
+   return err;
+}
+
+#endif /* PKCS_1 */
+
+
+/* $Source: /cvs/libtom/libtomcrypt/src/pk/pkcs1/pkcs_1_oaep_encode.c,v $ */
+/* $Revision: 1.4 $ */
+/* $Date: 2005/05/05 14:35:59 $ */