--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtomcrypt/src/pk/pkcs1/pkcs_1_v1_5_encode.c	Thu Jan 11 02:41:05 2007 +0000
@@ -0,0 +1,111 @@
+/* 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 pkcs_1_v1_5_encode.c
+ *
+ *  PKCS #1 v1.5 Padding (Andreas Lange)
+ */
+
+#ifdef PKCS_1
+
+/*! \brief PKCS #1 v1.5 encode.
+ *
+ *  \param msg              The data to encode
+ *  \param msglen           The length of the data to encode (octets)
+ *  \param block_type       Block type to use in padding (\sa ltc_pkcs_1_v1_5_blocks)
+ *  \param modulus_bitlen   The bit length of the RSA modulus
+ *  \param prng             An active PRNG state (only for LTC_PKCS_1_EME)
+ *  \param prng_idx         The index of the PRNG desired (only for LTC_PKCS_1_EME)
+ *  \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_v1_5_encode(const unsigned char *msg, 
+                             unsigned long  msglen,
+                                       int  block_type,
+                             unsigned long  modulus_bitlen,
+                                prng_state *prng, 
+                                       int  prng_idx,
+                             unsigned char *out, 
+                             unsigned long *outlen)
+{
+  unsigned long modulus_len, ps_len, i;
+  unsigned char *ps;
+  int result;
+
+  /* valid block_type? */
+  if ((block_type != LTC_PKCS_1_EMSA) &&
+      (block_type != LTC_PKCS_1_EME)) {
+     return CRYPT_PK_INVALID_PADDING;
+  }
+
+  if (block_type == LTC_PKCS_1_EME) {    /* encryption padding, we need a valid PRNG */
+    if ((result = prng_is_valid(prng_idx)) != CRYPT_OK) {
+       return result;
+    }
+  }
+
+  modulus_len = (modulus_bitlen >> 3) + (modulus_bitlen & 7 ? 1 : 0);
+
+  /* test message size */
+  if ((msglen + 11) > modulus_len) {
+    return CRYPT_PK_INVALID_SIZE;
+  }
+
+  if (*outlen < modulus_len) {
+    *outlen = modulus_len;
+    result = CRYPT_BUFFER_OVERFLOW;
+    goto bail;
+  }
+
+  /* generate an octets string PS */
+  ps = &out[2];
+  ps_len = modulus_len - msglen - 3;
+
+  if (block_type == LTC_PKCS_1_EME) {
+    /* now choose a random ps */
+    if (prng_descriptor[prng_idx].read(ps, ps_len, prng) != ps_len) {
+      result = CRYPT_ERROR_READPRNG;
+      goto bail;
+    }
+
+    /* transform zero bytes (if any) to non-zero random bytes */
+    for (i = 0; i < ps_len; i++) {
+      while (ps[i] == 0) {
+        if (prng_descriptor[prng_idx].read(&ps[i], 1, prng) != 1) {
+          result = CRYPT_ERROR_READPRNG;
+          goto bail;
+        }
+      }
+    }
+  } else {
+    XMEMSET(ps, 0xFF, ps_len);
+  }
+
+  /* create string of length modulus_len */
+  out[0]          = 0x00;
+  out[1]          = (unsigned char)block_type;  /* block_type 1 or 2 */
+  out[2 + ps_len] = 0x00;
+  XMEMCPY(&out[2 + ps_len + 1], msg, msglen);
+  *outlen = modulus_len;
+
+  result  = CRYPT_OK;
+bail:
+  return result;
+} /* pkcs_1_v1_5_encode */
+
+#endif /* #ifdef PKCS_1 */
+
+/* $Source: /cvs/libtom/libtomcrypt/src/pk/pkcs1/pkcs_1_v1_5_encode.c,v $ */
+/* $Revision: 1.2 $ */
+/* $Date: 2006/11/01 09:12:06 $ */