--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/pk/pkcs1/pkcs_1_v15_es_decode.c	Fri May 06 13:23:02 2005 +0000
@@ -0,0 +1,74 @@
+/* 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_v15_es_decode.c
+  PKCS #1 v1.5 Encryption Padding, Tom St Denis 
+*/
+
+#ifdef PKCS_1
+
+/**
+  PKCS #1 v1.5 Encryption Decoding
+  @param msg             The padded data
+  @param msglen          The length of the padded data (octets)
+  @param modulus_bitlen  The bit length of the RSA modulus
+  @param out             [out] Where to store the decoded data
+  @param outlen          The length of the decoded data
+  @param res             [out] Result of the decoding, 1==valid, 0==invalid
+  @return CRYPT_OK if successful
+*/
+int pkcs_1_v15_es_decode(const unsigned char *msg,  unsigned long msglen,
+                               unsigned long modulus_bitlen,
+                               unsigned char *out,  unsigned long outlen,
+                               int           *res)
+{
+   unsigned long x, modulus_bytelen;
+
+   LTC_ARGCHK(msg != NULL);
+   LTC_ARGCHK(out != NULL);
+   LTC_ARGCHK(res != NULL);
+   
+   /* default to failed */
+   *res = 0;
+
+   modulus_bytelen = (modulus_bitlen>>3) + (modulus_bitlen & 7 ? 1 : 0);
+
+   /* must be at least modulus_bytelen bytes long */
+   if (msglen != modulus_bytelen) {
+      return CRYPT_INVALID_ARG;
+   }
+
+   /* should start with 0x00 0x02 */
+   if (msg[0] != 0x00 || msg[1] != 0x02) {
+      return CRYPT_OK;
+   }
+   
+   /* skip over PS */
+   x = 2 + (modulus_bytelen - outlen - 3);
+
+   /* should be 0x00 */
+   if (msg[x++] != 0x00) {
+      return CRYPT_OK;
+   }
+
+   /* the message is left */
+   if (x + outlen > modulus_bytelen) {
+      return CRYPT_PK_INVALID_SIZE;
+   }
+   XMEMCPY(out, msg + x, outlen);
+   *res = 1;
+   return CRYPT_OK;
+}
+
+#endif 
+