--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/pkcs_1_v15_sa_decode.c	Tue Jun 15 14:07:21 2004 +0000
@@ -0,0 +1,77 @@
+/* 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 v1.5 Signature Padding -- Tom St Denis */
+
+#ifdef PKCS_1
+
+int pkcs_1_v15_sa_decode(const unsigned char *msghash, unsigned long msghashlen,
+                         const unsigned char *sig,     unsigned long siglen,
+                               int           hash_idx, unsigned long modulus_bitlen, 
+                               int          *res)
+{
+   unsigned long x, y, modulus_bytelen, derlen;
+   int err;
+   
+   _ARGCHK(msghash != NULL);
+   _ARGCHK(sig     != NULL);
+   _ARGCHK(res     != NULL);
+
+   /* default to invalid */
+   *res = 0;
+
+   /* valid hash ? */
+   if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) {
+      return err;
+   }
+
+   /* get derlen */
+   derlen = hash_descriptor[hash_idx].DERlen;
+
+   /* get modulus len */
+   modulus_bytelen = (modulus_bitlen>>3) + (modulus_bitlen & 7 ? 1 : 0);
+
+   /* valid sizes? */
+   if ((msghashlen + 3 + derlen > modulus_bytelen) || (siglen != modulus_bytelen)) {
+      return CRYPT_PK_INVALID_SIZE;
+   }
+
+   /* packet is 0x00 0x01 PS 0x00 T, where PS == 0xFF repeated modulus_bytelen - 3 - derlen - msghashlen times, T == DER || hash */
+   x = 0;
+   if (sig[x++] != 0x00 || sig[x++] != 0x01) {
+      return CRYPT_OK;
+   }
+
+   /* now follows (modulus_bytelen - 3 - derlen - msghashlen) 0xFF bytes */
+   for (y = 0; y < (modulus_bytelen - 3 - derlen - msghashlen); y++) {
+     if (sig[x++] != 0xFF) {
+        return CRYPT_OK;
+     }
+   }
+
+   if (sig[x++] != 0x00) {
+      return CRYPT_OK;
+   }
+
+   for (y = 0; y < derlen; y++) {
+      if (sig[x++] != hash_descriptor[hash_idx].DER[y]) {
+         return CRYPT_OK;
+      }
+   }
+
+   if (memcmp(msghash, sig+x, msghashlen) == 0) {
+      *res = 1;
+   }
+   return CRYPT_OK;
+}
+
+#endif