--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtomcrypt/src/pk/katja/katja_decrypt_key.c	Sat Feb 03 08:20:30 2007 +0000
@@ -0,0 +1,105 @@
+/* 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 katja_decrypt_key.c
+  Katja PKCS #1 OAEP Decryption, Tom St Denis
+*/  
+
+#ifdef MKAT
+
+/**
+   (PKCS #1 v2.0) decrypt then OAEP depad  
+   @param in          The ciphertext
+   @param inlen       The length of the ciphertext (octets)
+   @param out         [out] The plaintext
+   @param outlen      [in/out] The max size and resulting size of the plaintext (octets)
+   @param lparam      The system "lparam" value
+   @param lparamlen   The length of the lparam value (octets)
+   @param hash_idx    The index of the hash desired
+   @param stat        [out] Result of the decryption, 1==valid, 0==invalid
+   @param key         The corresponding private Katja key
+   @return CRYPT_OK if succcessul (even if invalid)
+*/
+int katja_decrypt_key(const unsigned char *in,       unsigned long  inlen,
+                          unsigned char *out,      unsigned long *outlen, 
+                    const unsigned char *lparam,   unsigned long  lparamlen,
+                          int            hash_idx, int           *stat,
+                          katja_key       *key)
+{
+  unsigned long modulus_bitlen, modulus_bytelen, x;
+  int           err;
+  unsigned char *tmp;
+  
+  LTC_ARGCHK(out    != NULL);
+  LTC_ARGCHK(outlen != NULL);
+  LTC_ARGCHK(key    != NULL);
+  LTC_ARGCHK(stat   != NULL);
+
+  /* default to invalid */
+  *stat = 0;
+
+  /* valid hash ? */
+  if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) {
+     return err;
+  }
+  
+  /* get modulus len in bits */
+  modulus_bitlen = mp_count_bits( (key->N));
+
+  /* payload is upto pq, so we know q is 1/3rd the size of N and therefore pq is 2/3th the size */
+ modulus_bitlen = ((modulus_bitlen << 1) / 3);
+
+  /* round down to next byte */
+  modulus_bitlen -= (modulus_bitlen & 7) + 8;
+
+  /* outlen must be at least the size of the modulus */
+  modulus_bytelen = mp_unsigned_bin_size( (key->N));
+  if (modulus_bytelen != inlen) {
+     return CRYPT_INVALID_PACKET;
+  }
+
+  /* allocate ram */
+  tmp = XMALLOC(inlen);
+  if (tmp == NULL) {
+     return CRYPT_MEM;
+  }
+
+  /* rsa decode the packet */
+  x = inlen;
+  if ((err = katja_exptmod(in, inlen, tmp, &x, PK_PRIVATE, key)) != CRYPT_OK) {
+     XFREE(tmp);
+     return err;
+  }
+
+  /* shift right by modulus_bytelen - modulus_bitlen/8  bytes */
+  for (x = 0; x < (modulus_bitlen >> 3); x++) {
+     tmp[x] = tmp[x+(modulus_bytelen-(modulus_bitlen>>3))];
+  }
+
+  /* now OAEP decode the packet */
+  err = pkcs_1_oaep_decode(tmp, x, lparam, lparamlen, modulus_bitlen, hash_idx,
+                           out, outlen, stat);
+
+  XFREE(tmp);
+  return err;
+}
+
+#endif /* MRSA */
+
+
+
+
+
+/* $Source: /cvs/libtom/libtomcrypt/src/pk/katja/katja_decrypt_key.c,v $ */
+/* $Revision: 1.4 $ */
+/* $Date: 2006/03/31 14:15:35 $ */