--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/pkcs_1_pss_encode.c	Mon May 31 18:21:40 2004 +0000
@@ -0,0 +1,122 @@
+/* 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 "mycrypt.h"
+
+/* PKCS #1 PSS Signature Padding -- Tom St Denis */
+
+#ifdef PKCS_1
+
+int pkcs_1_pss_encode(const unsigned char *msghash, unsigned long msghashlen,
+                            unsigned long saltlen,  int           hash_idx,
+                            int           prng_idx, prng_state   *prng,
+                            unsigned long modulus_bitlen,
+                            unsigned char *out,     unsigned long *outlen)
+{
+   unsigned char DB[1024], mask[sizeof(DB)], salt[sizeof(DB)], hash[sizeof(DB)];
+   unsigned long x, y, hLen, modulus_len;
+   int           err;
+   hash_state    md;
+
+   _ARGCHK(msghash != NULL);
+   _ARGCHK(out     != NULL);
+   _ARGCHK(outlen  != NULL);
+
+   /* ensure hash and PRNG are valid */
+   if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) {
+      return err;
+   }
+   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);
+
+   /* check sizes */
+   if ((saltlen > sizeof(salt)) || (modulus_len > sizeof(DB)) || (modulus_len < hLen + saltlen + 2)) {
+      return CRYPT_INVALID_ARG;
+   }
+
+   /* generate random salt */
+   if (saltlen > 0) {
+      if (prng_descriptor[prng_idx].read(salt, saltlen, prng) != saltlen) {
+         return CRYPT_ERROR_READPRNG;
+      }
+   }
+
+   /* M = (eight) 0x00 || msghash || salt, hash = H(M) */
+   hash_descriptor[hash_idx].init(&md);
+   zeromem(DB, 8);
+   if ((err = hash_descriptor[hash_idx].process(&md, DB, 8)) != CRYPT_OK) {
+      return err;
+   }
+   if ((err = hash_descriptor[hash_idx].process(&md, msghash, msghashlen)) != CRYPT_OK) {
+      return err;
+   }
+   if ((err = hash_descriptor[hash_idx].process(&md, salt, saltlen)) != CRYPT_OK) {
+      return err;
+   }
+   if ((err = hash_descriptor[hash_idx].done(&md, hash)) != CRYPT_OK) {
+      return err;
+   }
+
+   /* generate DB = PS || 0x01 || salt, PS == modulus_len - saltlen - hLen - 2 zero bytes */
+   for (x = 0; x < (modulus_len - saltlen - hLen - 2); x++) {
+       DB[x] = 0x00;
+   }
+   DB[x++] = 0x01;
+   for (y = 0; y < saltlen; y++) {
+      DB[x++] = salt[y];
+   }
+
+   /* generate mask of length modulus_len - hLen - 1 from hash */
+   if ((err = pkcs_1_mgf1(hash, hLen, hash_idx, mask, modulus_len - hLen - 1)) != CRYPT_OK) {
+      return err;
+   }
+
+   /* xor against DB */
+   for (y = 0; y < (modulus_len - hLen - 1); y++) {
+      DB[y] ^= mask[y];
+   }
+
+   /* output is DB || hash || 0xBC */
+   if (*outlen < modulus_len) {
+      return CRYPT_BUFFER_OVERFLOW;
+   }
+
+   /* DB */
+   for (y = x = 0; x < modulus_len - hLen - 1; x++) {
+       out[y++] = DB[x];
+   }
+   /* hash */
+   for (x = 0; x < hLen; x++) {
+       out[y++] = hash[x];
+   }
+   /* 0xBC */
+   out[y] = 0xBC;
+
+   /* now clear the 8*modulus_len - modulus_bitlen most significant bits */
+   out[0] &= 0xFF >> ((modulus_len<<3) - modulus_bitlen);
+
+   /* store output size */
+   *outlen = modulus_len;
+
+#ifdef CLEAN_STACK
+   zeromem(DB,   sizeof(DB));   
+   zeromem(mask, sizeof(mask));   
+   zeromem(salt, sizeof(salt));   
+   zeromem(hash, sizeof(hash));   
+#endif
+
+   return CRYPT_OK;
+}
+
+#endif /* PKCS_1 */